@Violistofhameln
I absolutely understand your shipper feelings, XD. After reading this chapter, I once again thought about the possibility of Ikumi/Tetsuo and came to the conclusion that it would be for the best for them not to progress into something romantic. If they did, I believe that the emphasis on accepting and overcoming one's trauma, be it partly or fully, will be lost to an extent.
We have seen Tetsuo's growth, how he came to terms with what he isn't and only afterwards began discovering who he is. His wound has closed, allowing him to begin his journey to establish where he can stand in the world of music. Ikumi, however, has yet to heal, both from the incident and from the abandonment. If he becomes Tetsuo's most special person, having him all to himself, it would only fill his wound, instead of stitching it up, hence he wouldn't be making any progress towards improvement.
On the other hand, people with PTSD need their "special person" in order to be "reintroduced" into the world. A therapist is a wonderful aid, but when the patient has already "imprinted" on someone, they have to play a part in the process. Not to mention that Ikumi was already showing signs of liking Tetsuo in that way when they were 12, but it could be attributed to his attachment after the trauma XD.
In the end, I think this story will have a stronger message, if romance isn't introduced, except for Yuriko and Tetsuro, whose relationship has been implied, as you said. Only when we see that Ikumi has grown as Tetsuo has, maybe after a timeskip, then maybe, just maybe, something along those lines wouldn't come off as negative obsessive behavior.