KanShin

KanShin is the slash ship between Kanji Kageyama and Eishin Kuga from the Twittering Birds Never Fly fandom.

Don't Stay Gold
Their first meeting occurs thanks to Yashiro, a yakuza leader, who calls Kageyama, a doctor of his acquaintance, to help him stop his underlings from getting into a fight with Kuga; Yashiro had ordered them to evict him from his apartment and kidnap him, but since the situation got out of hand he had to call for reinforcements. As the yakuza explains the situation to the doctor, he makes jokes about how the boy seems to be Kageyama’s type. The doctor, with his strength, punches the young boy in the stomach and knocks him unconscious. When Kuga wakes up, he is in Kageyama's infirmary lying on a cot, with Yashiro beside him. The doctor apologizes for the punch, to which the young boy replies by hitting him, while the yakuza asks him if he wants to start working for him; the boy refuses, then Yashiro leaves and entrusts the boy to Kageyama.

One morning a few days later, Kageyama and Kuga have breakfast together. Before he wakes him up, it is possible to notice Kageyama's interest in the visible scars on Kuga's chest, about which he talks to him shortly after. Kuga explains that they were made to him by his parents when he was still a child, and that they then abandoned him in an orphanage. Showing interest in the young man, the doctor also points out that he tends to stare a lot at people's faces, and Kuga jokes that it is because he finds his face cute and the doctor asks if in the orphanage he had learned to prostitute himself with other men; he doesn’t give a clear answer. During another meal, to be forgiven for badly cooked curry, Kuga lifts his shirt thinking the doctor was attracted to his body; Kageyama will explain that he has instead a fetish for scars and burns.

In a quick scene, Yashiro asks Kageyama how his relationship with the young man is going and Kuga tells him, lying, that they had sex. The doctor will later rebuke him and tell him not to behave like this with Yashiro, because according to him he "moves from one side to the other" (meaning that he can cover both a dominant and a submissive role, and that he could potentially acquire interest in Kuga). He also tells him not to stay shirtless in the house and, although Kuga initially jokes about it, in later scenes he is always visible wearing a tank top.

The first time the doctor clearly hits on the boy is when he shows his chest again claiming that the weather is too hot, and Kageyama lies down next to him with an erection pressing against his leg, that justifies claiming to be tired. A few days later Kuga surprises Kageyama calling a woman for a night meeting, showing himself jealous and not understanding his intentions. Kageyama explains that he only hit on him because he pitied his scars, and the boy leaves after punching him in the face and giving him the rent money he got as a 'part-time waiter'. Kageyama ends up not showing up to the meeting with the unnamed woman and realizes he is falling in love with Kuga.

While Kuga is somewhere away from home, Yashiro provokes Kageyama with the aim of making them reconcile, saying that he knows where Kuga is and that he would like to have sex with him. Kageyama gets information on his location and reaches him, while the boy once again knocks down some subordinates of Yashiro that the yakuza had sent to try to kidnap him again. Although he is initially upset to see the doctor and shows aversion to his request to go home, Kageyama kisses him and they end up having sex. As soon as they finish, they realize that Yashiro had provoked Kageyama to no avail, since he can't actually play a dominant role in bed and didn't really intend to do it with Kuga. The boy also reveals to the doctor that he is actually a virgin.

Main Series
The two characters in the following chapters are not very present, and rarely seen together. However, their interactions are very similar to those shown before, suggesting that their relationship has remained the same.

Fanon
Although the series focuses on the relationship between Yashiro and Chikara Domeki, the chapter 1.2, called 'Don't Stay Gold', is entirely dedicated to the development of their development. An animated short film released on March 1, 2021,  Twittering Birds Never Fly: Don't Stay Gold , helped them to gain popularity even among non-manga readers of the fandom.

On AO3, KanShin is the most written ship for both Kanji and Eishin and the second in the Saezuru Tori wa Habatakanai tag, after DouShiro.

Fandom
FAN FICTION

Trivia

 * In the animated transposition, when Yashiro tells Kageyama that he would like to have sex with Kuga, the doctor is shown much angrier than in the manga and he hits him in the face. In the manga, he just gives him a dirty look.