Is this the conclusion? This is from absolutely fucking nowhere, nothing got explained, why the protagonist time travel, the horrid shack painted with blood, why Sora has those strange eyes, the clue on the painting, nothing or I’m just missing something.
You missed everything, everything has been clued, the reason hinata regressed is because sora pleaded for help and it reached hinata (try to watch boku dake inai machi, its kinda similar plot with the mc regressed to the past and there was a reason he got sent to the past)
As for the painting, its the death motives filled by the corrupted hakuraku
The second volume is such a slog, the subplot of being of the teacher that want to separate the main characters is 100% crap+padding.
What a disappointment, the pacing and humor of the first part was so much better.