Sensei Lock-On! 2nd - Vol. 1 Ch. 4

[MangaDex]

 

[jimmysuzuki]

that last panel was gold, so manly

 

[SpecialProjectY]

Well, that's a bit odd... is he trying to sudoku his relationship since supposedly teacher+teacher relationship is kinda off the hook in the same school, although the other teacher has no problem whatsoever.