Yes, you play as a female transfer student vying for the affection of effeminate boys, and there are, at the very least, five pairs of male nipples that can be displayed at any time, but at the game's core is a secret fight club in which the shirtless lads duke it out during after-school hours. That's pretty much just like Street Fighter, right? It doesn't get any manlier than that.
Oh yeah, you don't actually trade punches with anyone in the game; instead, you beguile one of the fighters into inviting you to one of his backdoor bouts. Once there, you can cheer him on with the DS's mic to strengthen him and aid his attacks. You'll also be able to wipe him down afterwards in the locker room, toweling off his sweaty physique via a touchscreen minigame.
And if you want to take it further, but aren't sure how he'll react, after you've massaged all the knots out of his muscular shoulders, you can whisper breathlessly, a fraction of an inch away from his ear, "I have always admired you ... senpai," before running out of the room with a single tear trailing down your face.
That last feature might not be officially supported by Duel Love, but we're not going to let that get in the way of our completely heterosexual, red-blooded relationship with Yuki-san!