Keai Guominyuan

Yue Zhishi and Song Yu are brothers, but not related by blood. Yue Zhishi, who was fostered with the Song family since childhood, loves to cling to Song Yu, who is three years older than him, like a big brother. While Song Yu deliberately keeps him at arms length. Song Yu acts like an indifferent brother to his clingy puppy dog younger brother, but what others don't realize is that it is because he knows his own feelings so he has to restrain himself and keep away... Because Yue Zhishi is Song Yu's only allergen.
(Source: Kuaikan, translated)