We are all focused on Keichi and Shingo fight (it's normal because it's the main plot) but...

We are all focused on Keichi and Shingo fight (it's normal because it's the main plot) but I think chapter 10 is surprising because of Yuujin's attitude. I mean, remember he was the guy who wanted those two to break up ! Even if he's happy now in his love life, it's a big progress. He even tell Shingo "you can call me big bro" (thank you SuzukiLina for the summary) and take Shingo with him in his apartment because he doesn't want him to be left alone. Really surprising.
Obviously, there is something we don't get about Keichi's behaviour. Is he really a jerk or is he really hurt because he's sure that Shingo cheated on him with the photograph and think that Shingo finally never loved him...? Aaaargh ! I can't stand this situation.