Because Rein was a weak and simple beast tamer, he was expelled from the hero's group but that didn't stop his desire to be an adventurer. By taking simple quests afterwards he has a destined encounter with a strong cat girl.
Yuusha Party wo Tsuihou Sareta Beast Tamer, Saikyou Shuzoku Nekomimi Shojo to Deau
Because Rein was a weak and simple beast tamer, he was expelled from the hero's group but that didn't stop his desire to be an adventurer. By taking simple quests afterwards he has a destined encounter with a strong cat girl.