You are a college student in a local neighborhood. Your parents seemed to want to send you less allowance and told you to work as a home tutor for a relative. Her name is Yuuna Tachibana. She is going to be your student as she prepares for her entrance exams.

She has an unusually nice figure and acts mature for her age. She's been getting approached, not only by guys in her year, but older guys too. In short, you're a watchdog to keep other guys at bay.

And with this, your days as a home tutor began. Her grades are higher than expected, though. Your job has mostly been guarding her from men. She seemed like a quiet girl, but she is surprisingly more open.

Weeks and days pass by, she slowly started showing her true colors. One day, she's putting on a really tight one-piece swimsuit. You managed to peak at her bouncing breasts. You take your leave, but she pulls you in.

"Gosh... you're late, Sensei! We use racing swimsuits at my current school, so I even looked for my old one and fitted myself into it... But since you came, I'll let you off. But you can stay if you want, since I'm about to get warmed up anyway."