Canon
Byakuya Kuchiki: The only other shinigami in Anatole, and Kaien's captain in the absence of Ukitake. Kaien found out through Byakuya that he had died back in their world, and apparently by Rukia's hand. Byakuya seemed to hold some resentment toward him for his death and their relationship was rocky at best for the first several months. Kaien tried everything he could to befriend the younger shinigami, each attempt of which was met with resistance and resentment, particularly when Kaien paid his rent for him at the end of his first month, as he hadn't found a job.
After this, Kaien promised to leave him alone, and it wasn't until he had pulled back some that Byakuya allowed him in, just a little. Their relationship has been slowly improving, despite numerous setbacks, and Byakuya's even begun addressing him by first name. Kaien still hopes Byakuya will come to consider him a friend someday.
Scorched
Allen Walker: A friend of Lenalee's that he's spoken to a few times. His view on smiles and friendship was a comfort to Kaien during a period of depression, and Kaien just personally likes the young man's attitude and outlook on life.
Angeal Hewley: [Dropped] A man from a company called ShinRa. He seemed weak and disoriented when he first arrived in Anatole, and along with suggesting he see Sakura for treatment, they talked for quite a while in their first conversation over the Forge. He soon learned that the man was missing a weapon, and got him a broadsword, telling him a bit more about zanpakutou and shinigami when he came to deliver it.
They seemed to have quite a bit in common, and Kaien became very close to this man during his stay in Anatole. He was rather distraught when the man disappeared, and helped Zack comb the city searching for him.
Arthur Pendragon: Apparently a prince from a world called Camelot. They've only spoken a few times, but Kaien picked up on the loneliness vibe from Arthur and felt that he missed his home and the people in it a lot more than he let on. Kaien definitely wants to look out for him/be someone he can talk to if he needs it.
Cloud Strife: A man he spoke to over the network once, and then met once in person, he seems a bit of a loner and preferred to live out in the ruins than go into the city. Kaien found this a bit strange since Cloud apparently had friends in the city, but he didn't seem at all comfortable with the idea of staying with them.
Desmond Miles: [Dropped] A man that arrived in Anatole about the same time as he did, he introduced himself as "Michael" and told him he was a bartender back home. Always seemed a bit paranoid, and was a bit weirded out learning he was a death god, but he and Kaien always got along well. When he couldn't afford his rent, Kaien immediately offered him a place to stay at his apartment, (at which time he finally told Kaien his real name) and stayed with him and Namine for about another month before he disappeared during the week Kaien was incapacitated due to the bird-egg illness.
Elena: A Turk from the same world as Angeal and Zack, he enjoys her spunky attitude and work ethic, offering to let her make deliveries with him when she ran out of work to do.
Fai D. Flourite: [Dropped] A cheerful and friendly young man who was friends with Namine. He started watching Kaien after he said that he shared an one-bedroom apartment with Namine, even when he explained Namine slept on the couch (which may have made things worse?).
Haji: [Dropped] A mysterious man he only knew as Haji, the man came into Anatole looking for a girl called Saya, who was unfortunately not there. Kaien complimented him on his cello-playing soon thereafter, asking the name of the song, but Haji didn't remember it. They had a few exchanges afterward during a time that Kaien was feeling depressed and Haji attempted to offer some support/someone to talk to. It was disappointing that he disappeared before Kaien got to know him better.
Heine Rammsteiner: Heine came into Anatole with his clothes bloodstained and riddled with bullet holes. After confirming that the man was all right, Kaien proceeded to get him new clothes. They met again during an expedition into the ruins led by Leon, but haven't spoken much as of late. Heine is another of those loner-types that Kaien wants to help out of their shells.
Helen: A Claymore who's a friend of Priscilla's. They've only spoken a few times, but he appreciates her attitude and general outlook.
Itachi Uchiha: A friend of Naruto's. He greeted the man when he arrived in Anatole, and sent him the information post. And while Itachi was grateful and polite, he seemed rather dismissive of Kaien's attempts to be friendly and offer assistance. He's exhibited a similar personality as Byakuya in that sense, and while he's used to having his attempts at being personable and friendly rejected, it gets a bit frustrating at times. He really does wish Itachi would let him care more; unlike Byakuya, he hasn't made any progress since they met.
Karako "Game Fowl" Koshio: [Dropped] Once of the Deadmen in Anatole, he and Karako hit it off marvelously, sharing a similar personality and a friendship with Nagi. They occasionally shared lunch and a drink together, and Karako would often say that he must be something like Nagi's clone because of their similarly altruistic and hardworking natures.
Komui Lee: An unwitting stalker he has acquired by virtue of being a boy and friends with Lenalee. It's a good thing he hasn't heard of that blind date business some months ago. Keywords to this icon very relevant.
Lenalee Lee: A very nice girl who's a coworker of his at Nagi's ramen shop. They get along well due to having very compatible personalities, and they even ended up on a blind date once.
Leon Scott Kennedy: Another of those loner sorts that Kaien has been trying to get out of his shell, they talked several times in the first few months they were in Anatole, and even had lunch together a few times. In one particular instance, he insisted that Leon not spend Christmas alone, even though it was not a holiday that the shinigami themselves celebrated.
Mail "Matt" Jeevas: A tech-guy who's been in a world that wasn't his own before Anatole. He seems to prefer using text replies when talking on the network, though Kaien's heard his voice a few times. Matt was able to make a working version of the Soul Phone for him and Byakuya to track hollows with, as well as created a television and robot. He gets confused by Matt often though, because of the lack of technology in Soul Society, and currently thinks Matt can put a game "in" the Forge by shrinking it down and actually somehow getting it inside.
Mihael "Mello" Keehl: The info-post guy/loan shark of Anatole. He also seems to prefer text, or at least did for the first few months Kaien was here. He doesn't particularly care for the man's blase and disinterested attitude, and some of the things he said were enough to deeply shake his confidence at a time when a lot of his friends were disappearing. It's funny that he knows both Matt and Mello, yet doesn't know about the connection between them.
Minatsuki "Hummingbird" Takami: [Dropped] Another from the same world as Nagi, Kaien fell for her shy moe act hook, line, and sinker. He was worried when she came to Anatole with some serious injuries and considered her a friend. She wasn't in the city long before disappearing so Kaien never found out about her true nature as a violent psychopath or her deep trust issues, but he likely wouldn't have given up on their friendship even if he had known.
Mei Chan: A sweet little girl that he knows mostly through Namine. She apparently has healing abilities of some sort too, as she works at the clinic with Sakura.
Miranda Lotto: [Dropped] Another shy girl that Kaien met in his early days in Anatole. She was severely lacking in confidence, and Kaien always tried to encourage her and bring out the potential he saw in her. He became rather protective of the girl, and he was upset when she was one of the first of his friends to disappear.
Misa Amane: [Dropped] A cheerful and vibrant young girl who Kaien met when the messages about the serial killer were first appearing on Anatole's bulletin board. He quickly became protective of her when he learned she'd once been almost killed by a stalker, and during that week that the sun disappeared and the shared dreams were happening, he and Byakuya went over to her place for protection until Light came back to get her. He gave her a heart-shaped locket for Christmas that she could put a picture of Light in, and they even played in the snow together once. She, along with Light, have since disappeared.
Nagi "Owl" Kengamine: Kaien's employer at the ramen shop. He's a very kind and friendly man, and Kaien enjoys talking to him. He really appreciates that Nagi sets up celebrations for the Scorched every now and again, a chance for them to relax and enjoy themselves in the midst of all the hardships the Scorched have to endure. Since Anatole has proven itself able to bring the dead here, either from before their death or even beyond the grave (both of them found that they have died at some point in their universe), he really hopes the Door brings Nagi his wife someday.
Namine: A young girl that he came to know early on in his stay in Anatole. She seemed a bit shy and lonely when he first met her, and it bothered him that she referred to herself as a "Nobody," even if he really didn't quite know what that meant. Eventually, she came to live with him to make it easier for her to pay rent (though he would have been perfectly willing to let her stay for free), and he became rather attached and protective of her, thinking of her a bit as a little sister. He's sometimes a bit bothered that she doesn't entirely trust him enough to open up to him, but he's happy she can open up to Byakuya in that way. It also makes him happy to see the way Byakuya acts around her, because it's proof to him he's not as heartless as he tries to make himself out to be. Once, early on, they promised to be Byakuya's friends together.
Naruto Uzumaki: He first met Naruto when he was looking for instructors to teach self-defense at the dojo he was setting up, and then later found out Naruto was afraid of ghosts and zombies when there was a water zombie at the carnival. He also explained what it was shinigami do and found out Naruto held a grudge towards them for something that happened to his father. Kaien is still a bit unsure about it, and if he ever sees Ukitake again he plans to ask. While he's friendly to Kaien, doesn't seem to really trust him very much, but he's Byakuya's employer and so they interact semi-regularly. Kaien considers Naruto a friend and volunteers at the dojo despite already having a job at the ramen shop and working for the Patrol.
Oruha:[Dropped] A young woman he'd befriended around the beginning of his stay in Anatole. She had a lovely singing voice which he complimented her on, but she also often seemed a bit sad. He never pushed her to talk about it though, and she's long since disappeared.
Priscilla: The leader of the Patrol and a friend of Kaien's. He was one of the first to offer to take on extra shifts when the Patrol was still shorthanded in its early stages, and he offered to help take care of Priscilla's cat when she got it around Christmas-time. They've grown closer since, and their mutual desire to protect humans has been a point of bonding for them. She was someone he was able to confide in, a bit, during the time he was feeling depressed, and he's grown very fond of her, thinking of her a bit like a little sister, just as with Namine.
Riza Hawkeye: A woman from a human military. They first met when they went on an expedition into the mist after the kleptomaniac dolls led by Leon, and later spoke on the network a few times, talking a bit about duty and purpose. He hopes she's going to be all right, as he knows she's been through a tremendous loss recently.
Sakura Haruno: A friend of Naruto's and Anatole's resident healer. They've talked a few times and he considers her a friend. She also owes him a spar.
Turk Knife "Valeria" [Dropped] Another Turk. He'd befriended her during the week of no sun and suggested seeing Sakura for her headaches. He told her about his being a shinigami, and they talked about spirits and the different ways the cycle of life worked in their worlds. They spoke again when the carnival came to Anatole, and she told him to be careful about his planned venture into the mist with Byakuya and to contact a healer if necessary.
Xion: [Dropped] A shy girl who would always hide her face with a cloak. She was his partner on an extra Patrol shift he'd taken on for a brief while, but she disappeared soon afterward.
Zack Fair: He never had much interaction with Zack until Angeal's arrival, when the younger man seemed upset with him for getting Angeal a sword. While they didn't exactly get off to the best start, they have very similar personalities (and even look similar, both with black hair and blue eyes!), and Kaien helped him scour the city for Angeal when he disappeared and wants very much to forge a friendship with the young SOLDIER.