Kusuo and Kusuke have always been fighting with each other in terms of their abilities and intelligence. However, being a psi user, Kusuo always win towards the genius Kusuke. Kusuo always thought that his brother hated him about it but Kusuke corrected him that he didn't hate him at all and it was the opposite as Kusuke was obsessed of Kusuo. Kusuke is both sadistic and masochistic towards Kusuo because even though he knew he'd lost, Kusuke will still challenge Kusuo.
Kusuke cares deeply for his mom.
Like his brother, he is immune to Teruhashi's beauty. He also does't think she and Kusuo are a good match.