[Mutsuki] Ishiki no Kyoukaisen | The Ley Line of Consciousness (COMIC Penguin Club 2015-12) [English] {Hennojin}

To make sure there's no misunderstanding, towards the end of my previous comment, I was referring to my own experiences with the "Blood wasn't as dark despite the fact that no semen was involved" which means that with semen, it should be even more diluted.

I've had sex while on period before, and while I know it's surely different from case to case, it should be diluted quite a bit considering the blood wasn't as dark despite the fact that no semen was involved.