From Blissful Sin:

Yuuta lives together with his two step-brothers, Tomoaki and Takayuki. But their life together is far from a quiet one. So what happens when Yuuta gets angry one day because Takayuki won’t stop sticking to him? And how is Tomoaki involved in it? A story about a not so innocent brotherly love!

Keito, a high-schooler with an odd love of plants, finds a cosplaying babe in the garden. The babe in question is Roze, the reigning King of the Plant Kingdom! Roze is on the verge of extinction due to the lack of human affection. Only sex with Keito can restore his energy reserves and as Roze's kingly gaze heats up, Keito finds himself strangely compelled. "Join with me," Roze says. Why, the audacity of royalty! (Source: Blissful Sin)
Also includes the one shot Kiss Shite Master.