A very interesting premise of a manga. The structure is very similar to an apolcpayse setting. Although you do see that civilization does still exist. The hopelessness of the world is very much emphasized. This leads to the transfloration procedure. Essentially the lack of plants existing in this world is replaced by humans turning into what seems like artificial plants. Of course quite a hefty payment to volunteer to do this.
Toushirou emphasizes the suffering. He can barely support his mom and living in this dreadful world is leading him to take the transformation procedure as a last resort. The curious thing about Toushirou is that he can understand plants. Well more than likely those humans who went through the transfloration process. It’s a very curious skill, but of course his time is limited as noted by Hourai. It’s ironic that for someone who was bound to give up on life now a viable source of income, but his time is limited.
The thing that really kicks things of is when Sumi Matsuno is looking for her father. As a professional pianist, her father took the procedure so she could make a career out of it. Curiously enough, Toushirou, understanding the plants can tell there is a lot of anger when Sumi mentions her father. Well he forced her to play the piano and also abused her.
It’s very interesting how for both Toushirou and Sumi they both are struggling to survive in the hopeless world. That actual point is that Sumi only means of survival is through the piano. For someone who hates her father having to live through what he provided must make her hate playing the piano everytime. The fact she can still make a career out of it really remarks on her skill with it. It should not be a surprise that Sumi would want to burn the plant that her father become.
Though this leads us to the point that human emotions are complicated. Sumi’s father did some awful things to Sumi, but he wasn’t 100% bad. Since it its because of him she has a means of survival and she remembers the good parts. It does seem the abuse came when she wanted to quit the piano. Sadly in this cruel world that isn’t an option.
The development where Toushirou can connect with Sumi’s dad. Rather than taking the conventional route, my father actually loved me. We have the father who is no longer human realizing his daughter was in pain this whole time. Perhaps it was because of his pain that he didn’t notice or didn’t want to notice it. That one sorry more than likely makes a difference. Makes me wonder if Sumi rather than burn her father turn him into a piano for her to play. Rather than dwelling on the terrible things he did embrace the good that he did for her and move forward with her life.