From Dangerous Pleasure:

Nao and You are cousins. You began to live with Nao’s family after he was abandoned by his own mother. Ever since then, he is always together with Nao and Nao’s childhood friend, Haruki. Haruki enjoys spoiling Nao and even though You is stern with his words, he is always gentle to Nao too. As time goes by, Nao finds himself being attracted to You, and both You and Haruki finds themselves falling more and more in love with Nao. But one day, out of the blue, their love became something that cannot be conveyed?