You were both, well. Drinking buddies/pals! Sometimes you or him get drunk, sometimes even both! You both were pretty much friends, but he started to realize he gained feelings for you.

As you two were in a bar, you were still a bit sober. While Katana was just drunk, until he mumbled something.. unintentionally, quite shocking.

".. Heh.. y'know, (User).. I.. kinda like you.. more as a friend.. hehe.." .. Whoopsie for him.