Why do we seem to blackout a lot around Yumi ? Around everyone else except Maya, they go unnoticed. She doesn't even tell us of our memories like Maya says it causes blackouts. So I'm curious if something's special about her.
On that note, why do we blackout anyways ? Why learning about the past may cause problems, like making us "disappear" in the first place ?
Maya explains in one event that having too much of the memory jogged at once could cause issues. She even freaks out when it happens at one point. It's why she hates the fact that Noriko's back in the picture.
The fact that it happens a lot around Yumi indicates that there's some history between Yumi and Sensei that we do not yet know about, and it's important. Maya indicates that past versions of Sensei have fooled around with some of the girls in the past, so the reasonable assumption is that Yumi and Sensei were sexually linked in one of the past incarnations of Sensei. And Yumi seems to have a sense that something is off, because she has flat out asked him if he sometimes forgets thing (which immediately prompted him to have one of his blackouts). This is one of the big mysteries of the game, and is currently not explained.
What happened to Makoto in Bluejay ? I was surprised to see her jump, even more surprised to see her come back. Why did she do that ? The reset may have erased the whole event, but shouldn't everything leading up to her feeling suicidal stay ?
Sensei's eyes were closed the entire time, so what we see is somewhat unreliable. Either she never actually jumped, just dreamed of doing it, and was spooked by how close she got to doing it, or she jumped and someone/something intervened to undo it, and the memory of jumping is what caused her to be so spoked between that moment and the next reset.
Either way, she was utterly spooked, and somewhat broken, by the experience, and appears to have no memory of it after the reset.
Another option occurs to me, and that this may be a case of Makoto replaying (in her mind) an event from a past cycle. We do see hints of alternate past events elsewhere. During the second beach events, Sensei encounters a very submissive version of Yumi that bears no resemblance (beyond physical) to the one we see in game. There's speculation that this was a past cycle, that Sensei was remembering a past version of himself seducing her. If that's accurate, than Makoto could have relived an attempted suicide form a past cycle. This, also, would be adequate reason for why she's so spooked by the experience.
There are a few characters I don't recognize. There's one in the first reset, a girl who looks a lot more anime-ish compared to the rest of the game. There's one in a lot of different events, appearing very briefly as a static flash, I think she had very short grey hair with blue-ish eyes, I don't remember it well. Another one whom we meet at night when we got lost, and later she sells us watermelons at Maya's last event. Who are they ?
The first girl is a callback to a prior game Selebus started (Life is Beautiful? Nothing is Beautiful, I can't remember the name). I don't think she has any actual significance beyond that.
The second girl you mentioned is new to us, and we don't know any more about her than you do, aside from the fact that it's entirely possible to never meet her. Her first appearance is dependent upon sleeping with Sara, and her second is dependent upon sleeping with Ami, and since it's possible to avoid both, there may be a route where this character doesn't appear at all.
This is something that will likely to be explored more in Chapter 3, but at the moment, it's one of many unanswered questions. There are still two "side character" spots, so she may get promoted from easter egg to side character next chapter.
What exactly is or was our relationship with Maya ? What happened between us ? Why the two of us are the only people aware of the time loop ? Why does she hate Noriko ? The second beach event had a lot of hints but I couldn't tie them together so I'd appriciate it if someone could tell me the whole story.
They were lovers. This much we know. This is spelled out in Baby Finches.
At one point, before Sensei was a teacher, he was a tutor. Noriko was definitely one of his students, and even after Sensei abandoned Niki, Noriko was still secretly getting lessons from him. At some point, Maya started getting lessons from him as well, possibly because of her friendship with Ami. Whatever happened, they took to each other immediately, and soon after that, Sensei vanished from Noriko's life for the second time (the first being when he left Niki).
Maya is more worried for what Noriko represents than who Noriko is. Noriko knows a massive chunk of Sensei's life that Maya can't account for, and as mentioned above, recallling memories is DANGEROUS, and Noriko appears to be intent on reminding Sensei of ALL of it. This could cause Sensei to lose himself once again and start the process over (something we know has happened numerous times already). Most of the Maya events in chapter 2 are lore-heavy and provide a lot of this context, especially the dangers presented by memory recovery.