Ten'ou Ichika♀

Hajime's younger half-sister. She shares her brother's arrogant nature, but perhaps because she's still so young, her dignified nature is very lacking in contrast to her brother. She loves her older brother and shows hostility towards anyone else who has feelings for him. However, her brother doesn't regard her as a woman due to her immaturity, which is why Ichika wants to become a mature and refined lady as quickly as possible.

She loves receiving headpats and hates being spanked.

[From official website]