Onee-chan Maid no Gohoushi Time ~Himitsu Nan Dakara ne~

"You're my maid from today..." Hiroshi has an older sister named Mai, who is smart, good at sports, and beautiful. He can never resist her. One day, their parents have gone abroad to travel around. Hiroshi and Mai decide to have a battle and the loser will do all the housework. Even Hiroshi thinks that he will lose, but he luckily wins!

[Edited from ErogeShop]