Akihiko has 3 flags to become lovers, during ranks 4 (SPOILER)(deny the rumors and tell him not to misunderstand you), 6(SPOILER)(tell him he is becoming more awesome) and 9 (SPOILER)(tell him it's love). if you miss either of the first 2 flags, the third flag won't even appear.

Then you have to tell him yes. If you answer incorrectly on the this one, you will break the link (and his heart.)