Mushoku Tensei: Isekai Ittara Honki Dasu

Synopsis

After losing his fear of leaving his home thanks to Roxy, Rudeus starts playing outdoors by himself until he rescues a half-elf child, whom he assumes is a boy named Sylph, from a group of bullies. Sylph becomes friends with Rudeus and starts learning magic from him, and it is revealed Sylph is capable of casting magic without incantations as well. Six months later, Rudeus brings Sylph home during a storm and takes away Sylph's clothes by force so that they can take a bath together. However, he discovers that Sylph is a girl and her full name is Sylphiette. Despite Rudeus' apology to Sylphiette, she starts avoiding him, much to his chagrin. Sometime later, Sylphiette approaches Rudeus, and the two make up, with Rudeus determined to cherish the first true friend he has made in his new life.

(Source: Wiki)