Name ?

In the past I read this manga where girl meet a boy in high school and like fell in love with him and they draw sketch together but boy also like the mc but when boy was young he and his cousin were also his cousin’s parents die in car accident so she live with him and she said to promise her that he would never leave her but then the girl (boy’s cousin) went into coma after I guess she tried suicide and later boy also like mc but because of his cousin he never confess