@Rokermen
Minamoto is the only man Tsukiko tolerates and got close to. Why should she wait because Asahi "maybe" wants to be with him? Asahi turned him down already and for a long time she didn't even consider a romantic relationship with him (he was basically a sibling to her). It would be different if Asahi would openly tell Tsukiko that she likes Minamoto but afaik it never happened and she just keeps beating around the bush, wasting more opportunities to be with him.
Also, where will Tsukiko find another girly man who is willing to cross-dress for her...? ;D