Ane-san Countdown!  

Ane-san Countdown, 姐さんカウントダウン!, Anesan Countdown!

Riko umekita's life has been turned upside down by the scariest boy in her class, saruwada-kun. his family comes from a long line of yakuza and they don't mess around. when she was taken home with him, she found her parents there after some circumstances. then, saruwada-kun asked riko to marry him. it seems like something strange is happening.