Masato, weakness? No. Masato is the strongest. While everyone else is going crazy, Masato keeps doing what he always does.
Or, as I expressed it in my rant,
Masato may have been on Kyousuke’s team, but he’s never left Riki’s side. He’s never left anyone’s side. He didn’t like what Kyousuke was doing and he made that clear. He didn’t support the infighting. Nor did he change the way he treats anyone. He still challenges Kengo, he’s still Riki’s bro, leaving the room to give him and Rin some much-needed space. Masato is the one consistency in this route - apart from Riki’s trademark dedication. And consistency is reliable when the world around you is going crazy.
With Refrain knowledge, Masato’s behavior becomes even more understandable,
which I have briefly explained in Masato’s character topic (warning, spoilers).
