A: Because he wants to get the teacher's attention!
It's like an evil genius's plan right from the start! And only Mr. Tsuji doesn't see through it! You seriously can't help laughing at him, though. (In a nice way, of course.) After his wife tells him she wants a divorce, he's totally convinced that no one could possibly find a guy like him sexy; he's around 30 (so clearly past his prime), he's oblivious, a softie, too nice for his own good, and ultimately lonely. He believes in what's right but can sometimes be a bit of a pushover. The only one who knows the real Masaki Tsuji is Sohta (a.k.a. Evil Genius), who's been watching the teacher in silence. Then, in turn, I love watching Sohta as he tries to prove his love!
Yes, their relationship may have started with Sohta blackmailing Masaki, but his heart was totally in the right place (even if other parts of him weren't...)! He just wanted to comfort him and hold him and dry his tears! (It's not his fault he petted Masaki's other head... Or was that part of his Evil Plan™?)
The road to love is long and (very, very) hard... Will these two come... I mean... overcome the obstacles in their way!? Read to find out, and don't miss the sequel, "Listen to Your Teacher!" (Posted by Yao)