Miyu-chan wa Zutto Tomodachi

In the summer of his second year of high school, the protagonist, Yuushin Tahara, finds that his childhood friend, Miyu Fukagawa, who had moved away, has returned to the house next door. Although Miyu has grown up to be quite cute, there's something a little strange about her... This is a fresh and suspenseful romantic comedy about the gentle protagonist and his cute but rather quirky childhood friend, along with their friends and the adventures they get into!

(Source: Kadokawa, translated)