Knocking Up My Brother's Wife: My Sister-in-law Can't Resist My Seed

"Risa" has been friends with her neighbors, the Takeuchi brothers, for a long time. - Naturally, they were both into her. - Eventually, Risa married "Seiichi," the older of the two brothers. - The younger brother, "Ryuji," acted like he was happy for his brother, but a massive inferiority complex was simmering inside him. - One day, Ryuji hears from Risa that, due to Seiichi being infertile, they are unable to have children. - Until then, Seiichi, the golden child, had never experienced any setbacks in life. - If his first taste of failure came at this age, there's a chance he'd never be able to recover from it. - So, Ryuji makes a suggestion to Risa. - "I'll get you pregnant in place of my brother."​