To first give credit before grievances, the beginning is a solid intro as it readily conveys a character with a strong passion for art, yet also for appraisal and recognition, and quite arrogant too, but that's just how Fujimoto likes his women.
Unfortunately the oneshot falls completely in it's most important aspect of the relationship between the two main characters characters. A very important part of a tragedy is the set up before it, in order to make it a more compelling occurance. But right away the bond between the two characters is so sudden. One scene they just met and the next oh just the best of buds making manga together! And the rest of the relationship doesn't spend much time building upon that relationship to really convince the reader of how important these characters see the other. It should be convincing that it has to be that very character which completes the other very character, and that they couldn't be replaced with someone else in anyway, it has to be that person exactly. It's an interesting idea to show a relationship through dialogue-less scenes, to simply exist with ones company being enough, something somewhat explored in Fujimoto's other work "Goodbye, Eri" but that oneshot showed to the reader why those characters, for a lack of a better word, need each other. "Look Back" doesn't give that same amount of time, which to be fair there is an inkling of it, but before you know it someone's dead already.
Post death doesn't quite serve into the tragedy quite strongly and is maybe even weaker then the structure of the relationship, except one very poignant scene which will be discussed later. It very much takes away from everything to have the MC Fujino go down on her knees all "It was my fault!" which at the second reading was more offensive then the first. It doesn't show anything, it doesn't mean anything, and it's quite silly and cliché. It doesn't feel like a very honestly written reaction to the untimely death of a close friend, and this is more of a gut feeling but it doesn't even feel quite in-character, although I couldn't express properly why. The dream or what-if segment is quite confusing but it's to show the kind of thoughts one grieving has, if things could have just been different, if life was just a bit more ideal. I have no real opinions on this part, I think it's fine.
But the very VERY best scene comes after this, where Fujino talks about what a hassle drawing can be. And the question proposed by the unknown person is brilliantly answered in pictures only. She has always drawn for others in a selfish pursuit of popularity, being she was young and quite arrogant. The passion for art seemed lesser then gaining the interest and fame of her peers, and as such she threw it all away when she knew she couldn't achieve it anymore. Without further text then the question said, it is shown in quite a touching way that the reason why she still toils so is still for someone else, yet now out of a genuine interest in seeing how much someone can be awestricken and moved deeply by her work. The images of them together is made doubly compelling when one considers if this was her reason for drawing all this time, then her untimely death was the complete loss of will to continue her passion of art and creation. Yet something within that realization of why she draws was what reinvigorated her to get off hiatus and finish her manga, for whatever exact reason that may be can't be known and doesn't need to be known.
It is just so so close to being such a powerful oneshot that I can't help but lament for all that it lacks. I had no strong feelings towards the tragedy the first time since nothing was there to really show me why I should really care. Reading it again made the really moving parts better as I sat and thought about it, but the lacking parts even more egregious. I would love to see Fujino try his hand at another oneshot or even manga like this which leans more into sentimentality then comedy or action or whatever the hell happened in "Fire Punch".