Anticlimactic as fuck. I don't understand the point of the espers and there being 5 of them if the big bad was gonna off himself with the main character's help.
Just feels pointless.
Pretty sure it's meant to feel anticlimactic. The point of the story was never the whole plot about the five heroes going and defeating the big bad, it was about Naito and him dealing with his grief over Shimizu's passing. The story the two of them wrote together is a symbol of the two's relationship, so of course it won't get a flashy ending. Shimizu died, after all. Instead, the point of this scene is to show Naito finally being able to let her go and accept her death. Thus, putting the story to rest, content knowing that Tasuku was able to acknowledge it.