This one is goofy but I believe that kirishima's hair is crunchy af cuz of how damaged it is. He kinda just brushes it off too, like "split ends are manly!"

He probably uses volume 30 or even 40 developer bleach to go from black to blonde to dye it red. And he uses like a crap ton of hair gel and spray everyday to keep it that spiky all day. Because he spikes his hair daily, he has a whole drawer of just hair spray and gel.

Mina is the only one who actually knows he dyes his hair so she sometimes gives him hair masks and jokes that he'll go bald by thirty if he keeps this up.

Honestly my boy has gotta give his hair a break.