Spoilers for the anime are unmarked.
Rintaro is depressed and possibly suicidal.
He is often seen sad or bothered, but nobody around him seems to notice. Even in the ending theme, he stops smiling. In Episode 4, when his mom asks him if something is wrong, he denies it and says “I’m so hungry I could die.” There’s something off about the way he acts during this entire confrontation, but his wording could be foreshadowing or a hint of his true nature. And in official character descriptions, he is mentioned as losing confidence in himself and thinking of himself as a burden. Furthermore, the official description of Episode 5 says “Rintaro admits that he’s been a burden in more ways than one.” This is concerning, and possibly indicative of his character being depressed. People with depression often think of themselves as burdens.- Sort of confirmed. While not suicidal, Episode 5 reveals he's really unhappy that he might be burdening his parents since they're not related by blood; and Maki becoming more proactive in the team's training doesn't help, since he feels he's not doing his job as the vice-president.
- They may be setting Rintaro up to be a foil for Maki. In Episode 5, Maki confides in Touma about his abusive father. Touma comforts him and helps him. It’s in this same episode that Rintaro confesses that he feels like a burden and failure, also to Touma. But instead of comforting him or offering assistance, Touma yells at him and tells him others have it worse. He then tells him not to tell anybody. This may make him feel uncomfortable reaching out again, leading to dangerous repercussions. Where Maki has now had a weight lifted off his shoulders, Rintaro has now been made to hide the way he feels.
- Also, in Episode 4, Kaori states that “Useless people will turn away from that truth and continue to rot.” Rintaro calls himself useless in Episode 5, and is encouraged to get over it and hide his feelings. If this is connected, this may be foreshadowing that Rintaro’s mental health will continue to decline and get worse. Also, Rintaro is shown physically turning and looking away from his teammates more than any other character.
Maki’s father will harm or threaten Touma’s family later in the show.
After Kenji threatens to kill him, he asks for and receives Touma’s full name. He makes a comment about his parents. This may come back to bite him later, whether it be him physically assaulting somebody or blackmailing the Shinjous for money.