Well as of this chapter each of the characters has a problem, big or small.
Tarumizu, the MC: she's being taken for a ride by Nene. With her knowing about stuff between Nene and Amane, her problem is not asking why this is happening. Otherwise she's done nothing wrong.
Nene: we don't yet know about why she broke up with Amane. Her problem is exactly that, not being clear about her reasons, which leaves Amane to her inbetween state. If her affection for Tarumizu is genuine, good for her, if she's doing it to widen the gap between herself and Amane, well...
Amane: the most obvious one. Her problem is how she can't let go of Nene and can't decide what her relationship with her is. This leaves her in a perpetually unhappy state and open for...
Hayama: her problem is that she's a manipulative psychopath. She might have had a chance with Amane if she went about it normally, but she doesn't care about her feelings ("cry more") and only wants to possess her. Other people she sees as tools to hit Amane with. With the author hiding us details of the breakup still, it is a credible theory that Hayama caused it somehow. In short, she's a danger to everyone around her.