The series itself is just another excuse to do a chikan anime themed series, but the point of the 'association' adds a little to put something new at the category The fourth movie, all-lesbian one, seems the best IMHO. It goes away from the plotline from the other movies (moved by a student who wants help to get her teacher to her clutches) and the lesbian train scenes got the best of me and put this movie ahead of the others and many other train hentai stories I reccomend you to watch fourth movie first or even just see that movie if you don't want to seethe regular chikan thing appearing all over again