Yamada himself starts out as a Jerk with a Heart of Gold, but has generally become a nice guy by the time of the second witch war. He still has a couple of Character Check moments here and there where he may act a bit unreasonable, but he's usually pleasant to hang around with, and he's a sufferer of Chronic Hero Syndrome.
Shiraishi is friendly and caring all the time (save the occasional Innocently Insensitive or snarky comment), if not always good at showing her emotions clearly.
Hotaru is usually cheerful, and he's polite and pleasant towards others.
When Otsuka's telepathy alter ego doesn't rear its ugly head, she's a fairly nice and gentle girl.
Sarushima is one of the friendliest characters in the series and generally the most sociable, well-adjusted and accommodating of the witches (at least before Shiraishi gets some Character Development).
Alex has a slightly mischievous side to him, but other than that, he's an easygoing Mellow Fellow who's always in a good mood and up for hanging out with others.
Konno was originally really nice (to the point of being a people-pleaser) and becomes it again (though much better at standing up for herself this time) after Yamada helps her.
Kotori is so helpful that she borders on being an Extreme Doormat. Nobody is forcing her but she still protects her whole class against the powers of other witches, which comes with of having to constantly read their minds, when they're not even her friends. She also has a friendly and polite, if a bit cautious, attitude beyond that.
Chikushi can seem a bit aloof, but she's reasonably friendly to those who get to know her, and her Masked JK project certainly shows that she cares about others.
Even though Seishuin looks a bit threatening when she appears, she's a nice person and gladly cooperates with the student council so that Yamada can copy her power.
Downplayed with Kikuchi. She's stoic, rushed and not one for casual small talk, but still very polite and cooperative.
Himekawa is gentle, compassionate and puts others' well-being and injuries well before her own.
Arisugawa is generally very good-natured, though she can also be slightly mischievous and is a skilled manipulator.
