Sister's Friend Raw

I will keep your secret. Kyung-Soo has the prettiest older sister Oh Eun-Ah in her neighborhood. Byung-Tae, who has had a crush on Eun-Ah since she was young. Then one day, he learns Eun-Ah's secret, and Byung-Tae, who grasped her weakness, decides to stick to her instincts...