Aw, thank you very much! <3

I've been asked this question a few times, and I guess it would depend on interest if I were to do a second printing of the book. If it were to happen, I would take the opportunity to edit the mistakes I found in the two bonus chapters and probably add in the others or maybe the NSFW post-series piece. On the flip side, there wouldn't be any additional goodies to come with the second printing. Just the book. In addition to all this, I would need to ask my cover artist permission to do another release!

To summarize, it is possible, but I'm not prepared to release another round of preorders at the moment. :3 I do have a couple of other books in the works, including a full version of the Enshrined series, the Bound Together series, and a possible anthology print of a lot of my personal favorite SukuIta works.
I do

From personal interpretation, Yuji has always been a character who would put the lives of others before his own. He knew the risk of swallowing Sukuna's finger and did it anyway. He saved Megumi, then went on agreeing to carry the burden of Sukuna to ensure no one else got harmed. He could have floundered at the moment and curse the world, begging to be spared, but he doesn't. I admire that about him.
During the detention center arc, we see his determination to die his own way get tested, as he's put in a situation where he was about to die if Sukuna didn't step in. He then had to take his own life to save Megumi, again, dying prematurely to the fate he'd accepted for himself. This launches him into working harder to get stronger to ensure that he has some level of control over his death.
But during Shibuya... he loses that control again. He loses control over Sukuna, and comes to realize that he isn't powerful nor is it power that will define the control he has over himself or everyone else. Gojo is the strongest but he got sealed and people still died. Yuji is quite powerful, especially physically, but his friends keep dropping around him. He can't save everyone. Saving people can't be his goal anymore, it's fruitless as people will keep dying, so he needs to focus on killing curses. Focus on the cause of the problem. He's good for destruction, so let him destroy the things he hates the most.
Beyond that, if we go into manga territory, Yuji hasn't lost the spark to care. We see it when Megumi asks Yuji to save him, thus pulling him a bit out of his emotional rut. He's still self-sacrificial, as we can see when Yuji was more than willing to be killed by angel to free Gojo. And Yuji hasn't lost his will to help others as he tries to save those being attacked in the later half of the culling games, and vows to save Megumi again from Sukuna. I think this truly is an embodiment of his grandfather's dying words. Paraphrasing, but the idea of helping people, even if it's just one, ie. Megumi. And when it comes to Sukuna, Yuji was originally determined to take them both out with his execution. Now it seems Yuji is playing executioner or will have to reign the curse in, and whatever he's done during the time skip is in service to that. Sukuna was his original burden, it only makes sense that Yuji would do his damndest to see his fate through to the end.

I think the above thoughts came out a little messy, but all in all, watching this optimistic, hopeful, yet self-sacrificial character become someone willing to do anything to save others while also learning the desire to stay alive until his goal is complete. He continues to fight and get stronger to carry out his desires, and if he didn't have that drive to kill Sukuna and save Megumi, he would have given up a long time ago. The problem is that he still doesn't value is own life outside of what he can do with it in relation to others. He doesn't live for himself or see a future beyond this battle. That's heartbreaking to me.

Descriptions. I spend so much time looking for the write word or synonyms of a word I've already used or just pulling hair out because the scene feels like it's far too short and needs more detail and care. Action scenes and NSFW scenes are what I suffer with the most, though as much as I love writing dialog since it comes quite naturally to me, any dialog scene with more than three characters is an absolute mess to plan. Too many voices.

Characterization is a case by case basis for me. Some characters are harder to write than others. (For me, Yuji and Satoru are pretty easy, but Megumi and Suguru don't.) As for research, it really depends on how easily I let myself get distracted by what I'm reading about. XD