Onee-chan ga Kita
The story revolves around Tomoya Mizuhara, a 13-year-old boy who suddenly gains a big sister when his father remarries. 17-year-old Ichika is a little strange, and her affection for Tomoya is rather overwhelming, if not scary. On top of things, Ichika's friend Ruri is the ultimate sadist. Then there is Ichika's big-breasted quarter-Japanese friend Marina.
Source: ANN
Episode 1 - She Came! She Came!
Episode 2 - She Came to School!
Episode 3 - Big Sisters Came!
Episode 4 - Kouki the Tough Guy Came!
Episode 5 - Swimsuit Time Came!
Episode 6 - A Hot Guy Came!
Episode 7 - Christmas Came!
Episode 8 - New Year's Day Came!
Episode 9 - Valentine's Day is Coming!
Episode 10 - Valentine's Day Came!
Episode 11 - White Day Came!
Episode 12 - My Bedside Nurse Came!