What RemainsRegardless of whether Shinjiro dies or falls into a coma for the rest of the game, his sacrifice leaves a major impact on the lives of SEES' members. This is especially true for both Akihiko and Ken. Generally speaking though, the game takes a turn after his sacrifice and becomes much more serious and somber in tone. The members begin to question why they are fighting. Although I would argue most of the members took their responsibility seriously from the beginning, I think seeing a fellow Persona user and friend pass away (or go into what they are told is likely a permanent coma) forced them to realize just how real and dangerous fighting is. It starts a chain of events which either directly cause or may indirectly contribute to them coming to a resolution of why they are fighting.
Clearly, Akihiko is directly impacted by Shinjiro's sacrifice. He just lost his best friend of more than ten years who was also like an older brother to him. Shinjiro had always been Akihiko's rock whenever he started to lose himself. What would he do without him? If the female protagonist maxes out Shinjiro's social link, Akihiko goes to the hospital to talk to him even though there is a "no visitors allowed sign." If not or the player is being the male protagonist, Akihiko talks to Shinjiro at his memorial. Either way, Akihiko laments over Shinjiro's condition and begins to admit he has been too obsessed with power since Miki's death. He thought that as long as he was strong enough, he could protect anyone...but clearly he was wrong. He lost/may lose Shinjiro, too. Akihiko sobs and begs him not to leave him behind.
After pulling himself together, he stands up and says, "yeah, I know... Crying won't change anything, will it?" as if Shinjiro was about to speak. Much like Shinjiro would, Akihiko realizes he has things to do still which take precedence over his grief. Shinjiro wouldn't want him to wallow, anyway. Unlike Shinjiro, however, he uses his grief and respect for Shinjiro's sacrifice in order to press forward rather than drowning out the pain. He doesn't want to forget the emotions--he uses them as his strength. Shinjiro would be looking over him from the other side/hospital. Akihiko is then finally ready to let go of some of the guilt he had been carrying since the fire. His resolution ultimately allows Polydeuces to give rise to Caesar.
Once Akihiko has his resolve, he knows he must carry out his final promise to Shinjiro--to look after Ken. He finds him crouched in a back alley, commenting he looks half dead. Ken informs Akihiko that his mother's death is still on file as an unexplainable accident. Similarly, Shinjiro's death/coma was explained as being the result of a violent crime. No one will ever know the truth and he still finds himself being left behind. Akihiko says he will not drag Ken back to the dorm, but asks him to consider what meaning being left behind twice might have. Walking away, Ken admits that both Akihiko and Shinjiro were right. He really was just consumed by hatred. He was running away from the pain of losing his mother. Ken then decides he will no longer run away. He promises Shinjiro that he will see things through to the end, so he wouldn't have to worry about him anymore. Smiling, Ken tells his mother that he will be okay and says goodbye. Finding his resolution, Nemesis soon gives rise to Kala-Nemi.