Please help me find this:

An omegaverse manga. There were twins, one alpha (alpha-twin) and one omega (omega-twin). The alpha-twin was going out (not clearly stated 'tho) with his alpha-friend. One day the alpha-friend forgot his wallet and wenr back to school where he found the omega-twin having heat and raped him (and he pregnant). So the alpha-friend took responsibility and married the omega-twin. After that the alpha-twin went somewhere far away for years and later he came back when his omega-twin passed away.

Does anyone know what manga is this?
Thank you in advance!