Mucchi Muchi na Osananajimi ga Orenchi ni Sujitore shi ni Kita

'm just an ordinary college student, but I have a childhood friend who's one year younger than me. She's naturally clumsy and I can't help but look after her, so I've always doted on her like a real little sister. Her current problem is "losing weight gained from studying for entrance exams," so I've agreed to teach her how to do some strength training.. But wait.. isn't this.. a little too risky!? Curvy childhood friend x strength training = the ultimate x-c-c-c-t!?