I've just noticed that Saburo is missing but I'll add him and some Wikipedia links and maybe the relationship chart another day.
Also I didn't realise Kage was meant to be genderless. Of course, never explicitly mentioning someone's gender is much easier in Japanese than it is in English...
All names are Japanese order (surname first)
MONONOKE
Kage
A silver haired Mononoke who has become known as "Kage (Shadow)" due to constantly following by Yoshitsune's side haunting him since their life was saved by him. Has no gender, and has lived for over 100 years. Those other than Yoshitsune can only see their form on nights with a full moon.
Hiyori
A Mononoke who is with Kage as a protege.
Because her personality is brighter than Kage's, she is known as "Hiyori (Sunny)".
[*Hiyori literally means "weather", but with a kanji switch to emphasise the sun.]
En
A unique Mononoke with no physical form.
YOSHITSUNE'S ARMY
Minamoto no Yoshitsune
Ninth son of the late Minamoto no Yoshitomo, and Yoritomo's half-brother. Questions the sense of discrimination that exists in the space between the Mononoke, Mononofu and humans, and the significance of existence as a Mononofu. Because he possesses a pure heart, even as an adult he is able to see all Mononoke.
Satou Tsugunobu and Tadanobu
Brothers who are members of Yoshitsune's Shitennou*. Originally they worked for the Chinjufu Shogun of Northern Japan, Fujiwara no Hidehira and were following Yoshitsune in order to monitor him as spies, but soon had their hearts captured by him and vowed to share his fate.
[*Shitennou- "Four Heavenly Kings, in this case the four powerful warriors who are closest to Yoshitsune]
Musashibou Benkei
One of Yoshitsune's Shitennou. Possesses unparalleled fighting skills, and is also proficient in magic. Sealed Yoshitsune's power inside his body long ago. Rather than being warlike, on the contrary his personality is emotional, warmhearted and easily moved to tears.
Isesa Saburou
One of Yoshitsune's Shitennou, and the de facto leader. Has leadership ability and the discretion to make decisions with composure. Like Yoshitsune, he hates discriminating between people.
YOSHINAKA'S ARMY
Minamoto no Yoshinaka
Yoshitsune's cousin, later known as Kiso Yoshinaka. Because he has never been defeated, he is known as "The Demon God" or "The Demon Yoshinaka". Although he is part of the Minamoto clan, he is discriminated against and loathed by the main line for being part of a family branch with low status.
Tomoe Gozen
Excels at martial arts despite being a woman, and wields her lance spiritedly.
Supports and remains close to her lover Yoshinaka in both public and private.
Shida Yoshihiro
Originally connected with Yoritomo and Yoshitsune's siblings and Yoshinaka's father, and shared the family name, but after clashing with Yoritomo's armies due to his dissatisfaction with Yoritomo's rule of the eastern provinces, he took the surname Shida. After being defeated in the conflict with Yoritomo, he joined Yoshinaka's forces.
YORITOMO'S ARMY
Minamoto no Yoritomo
Yoshitsune's older brother. The rightful successor of the Minamoto clan, following the death of his father, Yoshitomo, he heads the family. He strongly believes the purpose of his existence is to purge all Mononofu other than the Minamoto clan, destroy the Taira, and revive the Minamoto clan.
Hojo Masako
Yoritomo's wife.
Having rightfully inherited the bloodline and power of the Hojo clan, she is a superhuman with an extremely high level of ability.
Kajiwara Kagetoki
Originally a commander of the Taira clan, at the battle of Ishibashiyama he saved Yoritomo by allowing him to escape.
From that time, he is a close and trusted associate of Yoritomo
Kazusa no Hirotsune
A vassal of Yoritomo's father, Yoshitomo, he was formerly a dauntless commander counted among the 17 Generals of Yoshihira. Perhaps because of his pride at leading an army of 20,000 men, his disrespectful and oppressive behavior towards the other vassals is conspicuous.