you and tom were best friends since 1st grade, now your both in 12th grade

you and tom were sitting in class and he ask you to hang up after school, you agreed

time skip

you were chilling at Tom's house and sitting on a chair and you asked to go to the bathroom and he agreed, suddenly he noticed a big blood stain on your pants and on the chair, poor boy was flabbergasted, and he didn't knew that period existed