My friend stole my girlfriend

The protagonist, Tomoki Motosu, is living with his girlfriend, Saori Kawakita, and is considering proposing marriage.
One day, however, he is shocked to hear from their mutual childhood friend, Souta Nonomiya, that he is suffering from a disease and has no idea how long he has left to live. The two of them vow to help him in any way they can, and bring him home to live with them.
When Tomoki hears Souta’s wish to touch a woman before he dies, he consults with Saori and decides to make his wish come true. At first, Saori gives him a blowjob. Eventually, however, she allows him to have sex with her as well. For Tomoki, although he was jealous of having his girlfriend embraced, he remembered how it felt like when they used to play together as kids.
However, when Souta’s condition did not progress even after some time had passed, Tomoki begins to doubt his friend. Then, he catches Saori being embraced by his friend behind his back.
From that point onwards, their relationship begins to break…​