The movie is a continuation of the relationship between Adachi (the virgin who at 30 discovers he can read minds) and Kurosawa (his work colleague secretly in love with him). The movie reverses things a bit. At the end of the series, Adachi was a virgin no more (this is all handled quite discreetly by the way) and at the beginning of the movie Adachi and Kurosawa haven't yet done "the deed" and so Adachi can still read minds. And so the movie proceeds from that point.
It's all very pleasant but frankly it's a bit boring. Make no mistake, Eiji Akaso and Keita Machada are still good in their roles and if you want to experience the "warm fuzzies" there are plenty of such scenes between the two of them, all presented with a romantic loving glow. But much of the humor from the series is absent and what drama there is still feels low stakes and easily resolved. But I'm sure fans of the series will be happy to see them together again albeit in the context of a rather weak plot.