Baka na Imouto wo Rikou ni Suru no wa Ore no xx dake na Ken ni Tsuite

Based on the erotic game by Pita Fetish!. To overcome his attraction for his younger sister Hana, Yuuichi Mitsui made sure to enroll at a university far away from his home. Unfortunately, being separated from her only strengthened his feelings. He continues to feel guilty for harboring illicit thoughts when suddenly, Hana shows up at his doorstep on a summer morning, looking more beautiful than ever. However, despite her physical maturity, her intellect is that of a child. Consequently, Yuuichi tries to hold back from laying a hand on his innocent sister. But it is easier said than done, especially when Hana's ignorance—combined with her innocence—makes her a woman that Yuuichi can't help but desire. (Source: MAL Rewrite)

Koikishi Purely☆Kiss THE ANIMATION

Based on the erotic game by Effordom Soft. Since childhood, our protagonist Kaname has always dreamed of becoming a Knight. After a near-fatal terrorist attack nearly killed both him and a new-found friend, they make a childhood promise that one day they’ll meet again in their quest to become splendid Knights that can protect others. Now, many years later, Kaname is about to enter a special school run by his father, where he and his younger sister Yuu (a big-brother-loving genius who skipped a grade to be with him) will be part of a special Knights-in training club called “Esquire”. On his way to school, though, he spots a mugging on the street from outside his bus window as they drove by, and with little hesitation he opens the bus window and jumps out of the moving bus to help. As part of the effort to solve this crime, he runs into the other heroines who will all eventually end up being the fellow members of Esquire. As the only boy in this club otherwise full of girls, will Kaname be able to fulfill his childhood promise? And will he and the “boy” with whom he made that promise ever meet again as they vowed?