Tiger & Bunny~ My Collection

Romantic relationship not yet established- shounen ai
Highly recommended (for fans of the series, this is really, really, REALLY good)

Warning: This one’s a real tear-jerker. This takes place after Kotetsu and Barnaby retire from being heroes in episode 25 and shows how they dealt with parting and being apart. This easily could've taken place.

Barnaby x Kotetsu (implied they may switch)
Recommended

Barnaby and Kotetsu struggle with their partnership ending and having to say goodbye. This story is a bit AU, as it infers they'd been in intimate relationship with each other. Very bittersweet and true to the characters personalities.

For fans of the series, this takes place following H-01's defeat, beginning when Kotetsu is about to be released from the hospital (recovering from injuries from that encounter).

Kotetsu x Barnaby
Highly recommended

This dj imagines extra scenes that take place during episodes 24 and 25 that acknowledges a budding romantic relationship between the two. This is very well written and should even please those who haven't watched the series.

Link: https://myreadingmanga.info/nightflight-tiger-bunny-dj-glow-eng/

Undetermined seme (though it would likely be Barnaby)
Recommended

A perverted NEXT's power has caused Kotetsu's body to link to Barnaby's in a strange way-- when Barnaby eats or drinks anything, Kotetsu feels strong sexual sensations. Barnaby has fun with this discovery at Kotetsu's expense... until Barnaby discovers he reacts sexually when Kotetsu does this...!

Very hot, smutty, and funny!

Seme/uke undetermined in Part 1
Recommended

AU- Kotetsu plays a multi-player online game called "King of Heroes" under the screen name "Wild Tiger". Eventually, a player who goes by the screen name "Barnaby" joins them and simply annoys the hell out of Kotetsu.

The players in his group decide to get together in real life to meet for the first time. Barnaby and Kotetsu get drunk, and then Kotetsu misses the last train, so he stays over Barnaby's and...

Barnaby x Kotetsu (A continuation of "LOGIN...?)
Recommended

Embarrassed by what happened after they got drunk and Kotetsu spent the night at Barnaby's place, both men distance themselves from each other and drop out of the game. However, Nathan (a player who goes by the name "Fire Emblem") not only schemes to get them back in the game, but also back into each others arms.

Recommended
A scene between Kotetsu and Barnaby that takes placed after episode 13, according to the mangaka. Nicely done, this will probably only be appreciated by fans of the anime.

Barnaby x Kotetsu
Recommended

Barnaby and Kotetsu have been hiding their feelings from each other. After being invited to the Kaburagi family home for New Year's, Barnaby finally makes a move. At first Kotetsu appears to be willing but then rejects him. After realizing Kotetsu was unsure and afraid of his own feelings, Barnaby decisively takes the lead for them both.

Kotetsu x Yuri (tease)
Highly recommended for fans of the TV series

Yuri finds Kotetsu in a dumpster and soaked from the rain, so he takes him to his office to warm up and dry off. Kotetsu is very depressed. Yuri's cold facade cracks a bit during this encounter.

For fans of the series, this takes place during the episode after Kotetsu falls off the monorail when his Hundred Power runs out prematurely while confronting the Lady Killer.

Kotetsu x Barnaby
Highly recommended

Kotetsu has a cold and Barnaby takes care of him. This may be a typical cliched plot, but this is done right. A perfect blend of sweet, hard sexy, and a very realistic portrayal of cuddling together.