Buster Keel!

Adventurers are individuals who embark on quests to defeat monsters, categorized by their combat styles such as Monster Users or Fighters. Keel, a young Adventurer, begins a journey to find Shiva the Monster User, renowned for defeating the S-ranked monster Dragon Ape. Keel believes Shiva took something valuable from him. In a town, he is told that Ravi, another Monster User, may know Shiva's whereabouts. Keel meets Ravi and her monster, Mippy, and decides to travel with her. The manga includes a bonus chapter in volume 9.