As someone who's obsessed with older sisters, I can't resist the sexy charm and unconsciously alluring big buttocks of my step-sister after bathing. (Takahashi Honami, DASS-517)

I'm a college student living with my older brother, and I have an intense "older sister" complex—it's to the point where I can only get excited by things related to my older sister. One day, my brother is going to move in with his girlfriend, Hono-chan. When I saw Hono-chan, who was even more beautiful and had a stunning figure than I'd imagined, I was incredibly excited. Hono-chan smiled and said, "I think I have a younger brother! Please call me older sister!" Wait, older sister? So my brother is getting married, which means she's my older sister now! My dream "older sister" has finally appeared, and I'm overwhelmed with excitement. But she's my brother's girlfriend, so I tried my best to control myself. However, after taking a shower, Hono-chan started stretching, revealing her incredibly alluring big butt, and even asked me for help. Faced with my sister's incredibly lewd big butt, how could I possibly resist…