Maigo no Onnanoko wo Ie made Todoketara, Genkan kara Detekita no wa Gakunen Ichi no Bishoujo deshita

One day, Yuusei Kuroda, an introverted high school student with zero dating experience, returns a lost little girl to her house... when the most beautiful girl in his grade, Ayano Shirakawa, appears! "As thanks for saving my sister," she begins to approach him boldly for some reason, and every day is filled with mishaps!? On top of that, a busty otaku classmate and an attention-seeking junior girl also appear, and his daily life suddenly becomes more glamorous!? A school romance comedy where fate changes as you suddenly become close to "the girl of your dreams!"

(Source: Kadokawa, translated)