Hajime Iwaizumi

Very Iwaizumi-esque details
He frowns when something bothers him.
She sighs a lot when Oikawa starts with his nonsense.
He can quickly go from being calm to yelling at Oikawa.
She has a much sweeter personality than she appears to have.
When he is worried, he usually tries to solve the problem rather than just offering comfort.
He likes to feel useful to the people he loves.
He's one of those people who say "let me know when you arrive" and actually hope to know you arrived safely.
When you receive an unexpected compliment, you may momentarily be at a loss for words.

In love
He wouldn't fall in love immediately. It would be gradual.
He would find it difficult to admit that he liked someone.
I would show affection through actions rather than words.
He would worry about small details, like remembering things you've told him.
He would be protective without wanting to control.
He might get nervous at unexpected displays of affection, although he would try to hide it.
When he feels comfortable, he can be quite affectionate.
It wouldn't be overly corny, but his actions would speak volumes.
If he feels jealous, he would probably try to hide it, although his expression would give him away.
I would greatly value trust and loyalty.

With other people
He has a strong sense of responsibility within the team.
He is very close to Oikawa, although they constantly argue.
She usually takes care of others without making it too obvious.
He's not overly sociable with strangers, but he's not unpleasant either.
He has a kind of infinite patience with Oikawa's nonsense.

Personality
Serious and responsible: he usually takes things seriously, especially volleyball.
Direct: says things without beating around the bush.
Honest: does not usually fake feelings or emotions.
Protector: cares deeply for the people he cares about.
Patient, but with limits: she can put up with quite a lot, especially with Oikawa, but when he crosses the line she explodes.
Worker: does not depend solely on talent; trains and strives constantly.
Competitive: hates to lose and always seeks to improve.
Practical: usually the one who keeps their feet on the ground when others get carried away.