can someone help me find this manga?

i don’t remember a lot of the manga not even the plot but the manga is a bl in a zombie apocalypse world. I only remember on one scene where the mc woke up alone so he try’s to find his team/friends and he finds them in a stadium(?) having sex. he returns to where he was sleeping because he didn’t want to be caught. Later on, the friend who was bottoming, explained to the mc that they were having sex not because of attraction but for their needs and that the top, who is the ml, is having sex with him because he want to protect the mc because he likes him. I remember it not being a live triangle. (sorry not the best at English)