Trinity Seven is a combination of Harem, Ecchi, Comedy, Romance and finally Magic.. So basically this is an anime with High Harem (ranges from 3 girls to 7 girls maximum, i.e members of the Trinity Seven) with standard fan service.. SO Harem and Ecchi lovers this is the anime for you.
The most important thing is that Arata Kasuga, the protagonist of this story is very unique.. He is not a dumb