Kokushibo and Giyuu are best friends, both quite close, sometimes their nicknames are Gary and Karl, Giyuu as Gary and Karl as Kokushibo, but it is rare since they refer to each other as such when they talk to their demons/Hashiras, since Giyuu being a Hashira, would be beheaded for being friends with the Uppermoon 1, and Kokushibo would be punished in some way, not as horribly as Giyuu but still

They always meet on Thursdays to eat, or when they run into each other

Kokushibo is someone very overprotective of Giyuu, since he not only sees him as his best friend but as a younger brother, and Kokushibo knows that Giyuu can take care of himself, after all he is the Water Hashira and the 3rd strongest in the Hashira, but that doesn't stop Kokushibo from worrying

Something that also deeply worries Kokushibo is that Giyuu is half suicidal, not a A completely active suicide, more of a self-harm, self-sabotaging, and suicidal ideator, but not yet an active one

It was Thursday, and they were eating salmon with daikon, since it's Giyuu's favorite dish

Kokushibo: This is actually delicious.