Itonami Itonamezu

The two haven’t done anything yet—their true selves are naive, they are innocent, and they have never thought about something like falling in love, even in a dream. On that day, the delicate, young girl working in the bento shop meets... This is the story about a boy and a girl who, innocent and with no experience in romance, suddenly begins their lives as newlyweds.
(Source: Chibi Manga)
Note: The chapter count includes one extra chapter.