Reki- Definitely a night owl. No doubt
Langa- It's difficult for me to decide. I think he'd be a morning person but I'm honestly not sure.
Kaoru/Cherry- Morning person. Yes he can stay up late but he likes being up early
Joe- Night owl. He likes being up late with his 'chicks'. He doesn't need to be up super early for his restaurant so he takes that time to sleep in
Miya- Night Owl. He stays up late playing video games. But then he also likes to be a 'responsible athlete' and goes to bed early. He can stay up when he really wants to play this game but when he needs to be responsible then he goes to bed.
Shadow- I honestly cannot decide at all. I can see him being more of a Night Owl though... I think it makes a lot of sense for his character.