Endless Rain (manga)

Akira lived a life of happiness with his gentle mother and little brother despite the fact his mother was the mistress of the committee head of the Kasuga Foundation. When his mother dies unexpectedly, he and his brother are moved to the headquarters of the Kasuga Foundation and put under the mercy of Hyogami, his father's proxy. Akira is desperate to protect his brother from the scandalous nature of their births no matter the cost. But, Hyogami's demand is Akira himself!