i'm sorry but i dont quite get it, so the kid calls his father "Raion-san"? i dont underst...

Maybe he is not the father

Taiga was explaining to Kiri that Raion is his father real name. Since Raion is also the pronunciation of Lion in Japanese so Kiri got confused. Of course he had to add san as well to show some respect for his father. He didn't seem to like his father that much because he used san, not otousan. The future chapters will explain their relationship deeper.

Thanks I didn't quite get it either