18+ Himawari to Hitsujitachi!

Kazuma has always lived a normal life until one day, Himawari Sakuya suddenly enters his life and claims that he is her brother and that he is next in line for the family inheritance. Sakuya, with her princess attitude, is apparently from a very rich, prestigious family and has come to take Kazuma back to the estate. Until he decides to become a member of the Himawari family, Sakuya and her maid Torako decides to live with Kazuma. Little does he know, Sakuya is being hunted down by a mysterious group.

(Source: MU)