Finished series: Asu no Yoichi!

...him anything new, so his father sends him off to train in the city -- at the dojo of the Ikagura family, who use the same style. It just so turns out that the father and mother have left ('on ... rule of anime is to get rid of the parents!) and so Yoichi is taken in by the four Ikagura sisters. Obviously, one boy who doesn't know anything about the modern world surrounded by four girls is just asking...