The thing about Steins;Gate Onshuu no Braunian Motion is that, as a standalone manga, it's really mediocre. It only has genuine value, and what it brings to the reader can only be brought forth if that reader has at least watched the S;G anime. Tbh I'd go as far as saying that the minimum is playing the VN and completing all the routes (Essentially 100% completion); that's how contextually dependent this manga is.
Still, inspite of this glaring limitation, Steins;Gate: Onshuu no Braunian Motion is able to tell an engaging story that gives much needed depth and characterization to the most criminally underused character of S;G: Yuugo Tennouji. This manga's story is essentially Tennouji's backstory, and it doesn't suffer from this nature because of its short length.
But the thing about the story is that, while compelling on its own, it wouldn't work the way it does were it not for the characters. More importantly, its how the mange explores Tennouji's past with his family and Amane Suzuha that stands out, at least to me. I think the reason for that is because they were made to interact in such a way that, for people fond of S;G everything feels nostalgic and bittersweet. I think the strongest example of that came with how the manga handled the confrontation between Okabe and Yuugo and the new perspective that it gave us. Its able to evoke genuine empathy in readers, or at least in me.
The weakest aspect of the manga has to come in the form of the art, specifically the switch in artist between volumes. It just doesn't feel right to me, and it's unfortunately the single greatest issue with all manga adaptations of S;G. Independent of one another, both artists to a great job. Though I must say that the better style is that of the second volume, done by Yoshida Tadasu. The key factors in this are the character designs, the super thin lines, the facial shading and his use of screentones and overlays.
I really enjoyed reading this manga, but I think it's because I can easily overlook its flaws and shortcomings. I think that has to do with me having had consumed all S;G related media before reading it. It was something I never knew I always wanted and also really needed.
