User blog comment:Noramehablia/red eyes/@comment-124.178.120.144-20170422063503

Red eyes normally comes across in a state of pure anger of another emotion that has been intensely enhanced depending on the situation the character is in, that's why Erza has been known for her death glares.

Matsu however, in accordance with the dragon cry movie, I assume that part of his dragonification during the movie.