Board Thread:General Discussion/@comment-4435241-20191001200320/@comment-28224025-20191025190729

Then Irina gets big and buff.

STR INT battle witch build.

It's more of a personal, closer bonds thing, I'd say. He's that one main boy close to everybody.

Like, Miyano calls Haizaki "Ryouhei" and Haizaki calls her "Akane". Tenma calls Nishizono "Shinsuke, etc. It's usually because they are specifically close in friendship or related.

Both Tsurugi and Haizaki called their main rivals by their second names, since they weren't that close yet.

Endou is another talk, but I assume it would also have something related to family, respect, etc.