Bah, this is my own fault for making the request when I'm still waking up and not explaining the whole situation fully. Apologies.

Prior to having those memories erased, San felt guilty for being unable to stop two friends he met (that being his first vessel, Conleth, and a nurse, Cathrin) from committing suicide when he came back to above after his second war. He was depressed and grounded from taking any other missions due to being emotionally compromised for several years. Eventually, Enos took pity on him and erased his guilt along with several memories involving the two humans.