About time for a masterpost, I'd say
Please note that everything written here is completely fictional, and contains mostly explicit adult content, most of which happens between dudes. You've been warned.
KAT-TUN
NTT
Mind Games
Boys from Nowhere
Undercover Work
Endurance Limit
Heavy Petting
Becoming
Sound and Vision
Traditions
Radio Silence (Or a Lack Thereof)
Diplomacy Skills
Just Right
Cutting Edge
A Pirate's Life For Me
Indulgences
Sounding Off
O Green World, Part I; Part II
Animal Crackers
The Way The Cookie Crumbles
Stick Shifting
If You Can't Beat Them...
Making Ladies
Regulation (Or, a True OG)
Interloper
Three is a Magic Number
Playing Games
Junno/Koki
Instruments of Fate
Strawberry Fields Forever
Signal
Inked Imaginings
Hanging Around
Solicitations
B-Sides
Plug In Baby
Game On
Patience and Other Virtues
What the Water Gave Me
Silence of Fireflies
Magic Moment
Relaxation Methods
School of Hard Knocks
(are you ready to) Bite Me
When Things Get Rough...
Metronome
Sweet Dreams
A Friend in Need
Chain of Love
Idle Thoughts
Cuff Me If You Can
Curiosity
Parasite
Down the Rabbit Hole
Doggy Boys
A Cheeky Sort of Fellow
Trivial Pursuit
Surprise Presents
Untitled
Step the Stage and Take Control
The Stranger
Mutually Assured Distraction
Nakamaru/Koki
Only Fingerprints
All Night Long
Distractions
Standing Orders
Information Gathering
Pictures of You
Needlepoint
In the Line of Fire
Tug of War/War of Attrition
Rough Handling
Rough Handling, continued
Untitled (+Kame)
A Helping Hand
Nakamaru/Junno
Not So Grimm
Stay Within My Voice
Propositional Phrases
Tactical Trolling
Honour and Other Lofty Ideals
Reward System
Picture Perfect
Foxtrot Uniform Charlie Kilo
Private Game
Nakamaru/Ueda
The Sacrament
Change of Air
Slow Voice on a Wave of Phase
Breathing Room
Shooting Star
Ueda/Koki
Squeaky Clean, +Nakamaru
Endurance Exercises
Night Work
Yank Your Chain
Nakamaru/Jin
Booty Call
Long Distance Call
Untitled
Kame
Rough and Tumble, Kame/Koki
Like A..., Kame/Koki
Doggy Style, Junno/Kame
With the Quickness, Kame/Koki
Hot Coffee, Kame/Koki
I Wanna Be Your Dog, Kame/Koki
Untitled, Nakamaru/Kame
Fun in the Sun, Maru/Ueda/Junno/Kame/Koki
Free Time, Kame/Junno/Maru/Ueda/Koki
Double Vision, Koki/Koki
Let Them Eat Cake, Kame/Maru/Junno/Koki/Ueda
Service With a Smile, Ueda/Maru/Junno/Koki
Bang Out, Kame/Maru/Junno/Koki/Ueda
Mirror Match, Nakamaru/Nakamaru +KAT-TU
The Odyssey, Nakamaru/various
NEWS
Flirts in Skirts, TegoMasu
Memoirs, Kato Shigeaki/Masuda Takahisa
All Eyes on Me, TegoMasu
Dirty Boys, TegoMasu
The Art of Legilimency, Kato Shigeaki/Koyama Keiichiro/Masuda Takahisa/Tegoshi Yuuya
Kis-My-Ft2
The Quiet Game, Fujigaya Taisuke/Kitayama Hiromitsu
Perchance To Dream, Fujigaya Taisuke/Kitayama Hiromitsu
Kanjani8
Shady Dealings, Yasuda Shota/Ohkura Tadayoshi
Inter-Group
Red Right Hand, Ohkura Tadayoshi/Taguchi Junnosuke
Sleepeasy, Ohkura Tadayoshi/Taguchi Junnosuke
Weekend at Kame's, KAT-TUN/Kis-My-Ft2
Slippery When Wet, Miyata Toshiya/Taguchi Junnosuke
Chasing Waterfalls, Kamenashi Kazuya/Tamamori Yuuta
Doubleheader, Kitayama Hiromitsu/Ohkura Tadayoshi
Full Service, Nikaido Takashi/Tanaka Koki
Key of Life, Kame/Massu
Highschool Quest, Fujigaya Taisuke/Tanaka Koki
Call Me Maybe, Massu/Junno
Smile Maker, Massu/Maru
Hell-Bent for Leather, Koki/Pi
I Feel Pretty, Koki/Tegoshi
Aural Fixation, Massu/Maru
Home Alone, Massu/Maru
Where the Green Grass Grows, Taguchi Junnosuke/Ohkura Tadayoshi
Pitching a Tent, Maru/Tegoshi
Fish Out of Water, Massu/Maru
Through The Grapevine, Massu/Junno
Right to Remain Filthy, Koki/Tegoshi
The Hunger Games, Massu/Ryo
For Your Reference, Massu/Maru
Oracular Spectacular, Nakamaru/Massu/Tegoshi
What the Guys Go Crazy For, MassuPi
Dinner and the Eiffel Tower, Tegoshi/Kame/Massu
Wake Up Call, MassuPi
Undisclosed Desires, Massu/Maru
After the Show, PiMaruKoyama
Swagger, MatsuJin
Bucket Seats Have All Got to Go, Pi/Akkun +Ryo, Jin
Cravings, Jin/Meisa
Drama Fic
Out of the Frying Pan, Kitajima Daichi/Tetsuka Yutaka, Rescue
Take Him Down a Peg, Ranmaru/Machiko, Legal High
Favors, Ranmaru/Machiko, Legal High
Leisurely Pursuits, Seishirou/Miroku, Yuukan Club
Meeting with the Boss, Yukari/Keigo, Last Money
KAT-TUN
NTT
Mind Games
Boys from Nowhere
Undercover Work
Endurance Limit
Heavy Petting
Becoming
Sound and Vision
Traditions
Radio Silence (Or a Lack Thereof)
Diplomacy Skills
Just Right
Cutting Edge
A Pirate's Life For Me
Indulgences
Sounding Off
O Green World, Part I; Part II
Animal Crackers
The Way The Cookie Crumbles
Stick Shifting
If You Can't Beat Them...
Making Ladies
Regulation (Or, a True OG)
Interloper
Three is a Magic Number
Playing Games
Junno/Koki
Instruments of Fate
Strawberry Fields Forever
Signal
Inked Imaginings
Hanging Around
Solicitations
B-Sides
Plug In Baby
Game On
Patience and Other Virtues
What the Water Gave Me
Silence of Fireflies
Magic Moment
Relaxation Methods
School of Hard Knocks
(are you ready to) Bite Me
When Things Get Rough...
Metronome
Sweet Dreams
A Friend in Need
Chain of Love
Idle Thoughts
Cuff Me If You Can
Curiosity
Parasite
Down the Rabbit Hole
Doggy Boys
A Cheeky Sort of Fellow
Trivial Pursuit
Surprise Presents
Untitled
Step the Stage and Take Control
The Stranger
Mutually Assured Distraction
Nakamaru/Koki
Only Fingerprints
All Night Long
Distractions
Standing Orders
Information Gathering
Pictures of You
Needlepoint
In the Line of Fire
Tug of War/War of Attrition
Rough Handling
Rough Handling, continued
Untitled (+Kame)
A Helping Hand
Nakamaru/Junno
Not So Grimm
Stay Within My Voice
Propositional Phrases
Tactical Trolling
Honour and Other Lofty Ideals
Reward System
Picture Perfect
Foxtrot Uniform Charlie Kilo
Private Game
Nakamaru/Ueda
The Sacrament
Change of Air
Slow Voice on a Wave of Phase
Breathing Room
Shooting Star
Ueda/Koki
Squeaky Clean, +Nakamaru
Endurance Exercises
Night Work
Yank Your Chain
Nakamaru/Jin
Booty Call
Long Distance Call
Untitled
Kame
Rough and Tumble, Kame/Koki
Like A..., Kame/Koki
Doggy Style, Junno/Kame
With the Quickness, Kame/Koki
Hot Coffee, Kame/Koki
I Wanna Be Your Dog, Kame/Koki
Untitled, Nakamaru/Kame
Fun in the Sun, Maru/Ueda/Junno/Kame/Koki
Free Time, Kame/Junno/Maru/Ueda/Koki
Double Vision, Koki/Koki
Let Them Eat Cake, Kame/Maru/Junno/Koki/Ueda
Service With a Smile, Ueda/Maru/Junno/Koki
Bang Out, Kame/Maru/Junno/Koki/Ueda
Mirror Match, Nakamaru/Nakamaru +KAT-TU
The Odyssey, Nakamaru/various
NEWS
Flirts in Skirts, TegoMasu
Memoirs, Kato Shigeaki/Masuda Takahisa
All Eyes on Me, TegoMasu
Dirty Boys, TegoMasu
The Art of Legilimency, Kato Shigeaki/Koyama Keiichiro/Masuda Takahisa/Tegoshi Yuuya
Kis-My-Ft2
The Quiet Game, Fujigaya Taisuke/Kitayama Hiromitsu
Perchance To Dream, Fujigaya Taisuke/Kitayama Hiromitsu
Kanjani8
Shady Dealings, Yasuda Shota/Ohkura Tadayoshi
Inter-Group
Red Right Hand, Ohkura Tadayoshi/Taguchi Junnosuke
Sleepeasy, Ohkura Tadayoshi/Taguchi Junnosuke
Weekend at Kame's, KAT-TUN/Kis-My-Ft2
Slippery When Wet, Miyata Toshiya/Taguchi Junnosuke
Chasing Waterfalls, Kamenashi Kazuya/Tamamori Yuuta
Doubleheader, Kitayama Hiromitsu/Ohkura Tadayoshi
Full Service, Nikaido Takashi/Tanaka Koki
Key of Life, Kame/Massu
Highschool Quest, Fujigaya Taisuke/Tanaka Koki
Call Me Maybe, Massu/Junno
Smile Maker, Massu/Maru
Hell-Bent for Leather, Koki/Pi
I Feel Pretty, Koki/Tegoshi
Aural Fixation, Massu/Maru
Home Alone, Massu/Maru
Where the Green Grass Grows, Taguchi Junnosuke/Ohkura Tadayoshi
Pitching a Tent, Maru/Tegoshi
Fish Out of Water, Massu/Maru
Through The Grapevine, Massu/Junno
Right to Remain Filthy, Koki/Tegoshi
The Hunger Games, Massu/Ryo
For Your Reference, Massu/Maru
Oracular Spectacular, Nakamaru/Massu/Tegoshi
What the Guys Go Crazy For, MassuPi
Dinner and the Eiffel Tower, Tegoshi/Kame/Massu
Wake Up Call, MassuPi
Undisclosed Desires, Massu/Maru
After the Show, PiMaruKoyama
Swagger, MatsuJin
Bucket Seats Have All Got to Go, Pi/Akkun +Ryo, Jin
Cravings, Jin/Meisa
Drama Fic
Out of the Frying Pan, Kitajima Daichi/Tetsuka Yutaka, Rescue
Take Him Down a Peg, Ranmaru/Machiko, Legal High
Favors, Ranmaru/Machiko, Legal High
Leisurely Pursuits, Seishirou/Miroku, Yuukan Club
Meeting with the Boss, Yukari/Keigo, Last Money