Do u know this manga???

I remember reading this manga about a high school couple,the couple has sex like a lot of couples do but one day this random girl ask him if he can do her if and he said ok so they do it (I dont think he sees sex as a big deal considering that he was thinking about his girlfriend while doing it) she had blonde hair and he had black hair,I dropped it once I read that bc I was so f*u king anger but um curious to see how it ends