Tensei shitara Ken deshita

A man dies and awakens in another world not as a warrior or mage, but as a sentient sword. Able to move with telekinesis and absorb skills from the monsters he defeats, he spends his new life growing stronger until an accident leaves him stuck and unable to continue alone. His wielder finally arrives in the form of Fran, a young Black Cat beastkin escaping slavery. With the sword's power, she wins her freedom and names him Shishou, or Teacher. The two become an unconventional master-and-student pair of adventurers, pursuing greater strength for a deeply personal reason: Fran wants to achieve the evolution no member of her tribe has ever reached.