I absolutely love how Fuyuki is taking all of this in stride (well, as level headed as one can be in this situation) and how she composes herself. Power to you, girl.
I read the available raws so far. Part 1 of chapter 4 just dropped today, but it seems that Chaosteam is translating a chapter when both parts are out (good choice), which means chapter 3 is due anytime.
For those who are more spoiler hungry, you can read about chapter 3 & 4.1 below (also, this is by memory because the site has taken down chapter 3 LOL so apologies for any minor mistakes):
The mysterious senpai is Fuyuki’s high school senpai. It turns out that Fuyuki is a year younger than Kyouhei and Eri, and she went to a different high school from Eri. We can see that the senpai and Fuyuki are somewhat close, but there’s a reasonable amount of room for doubt. When Eri introduces herself, the senpai seems to know about her (implying Fuyuki used to talk about her). The senpai quickly takes her leave after introductions without stirring up any sort of trouble or drama.
Meanwhile, as Eri and Fuyuki have their coffee together, Eri starts asking about the senpai, getting upset that she didn’t know of her existence. Fuyuki is a little perplexed by this because she believes it’s only natural that Eri didn’t know about the senpai since they went to different high schools. Eri doubles down and is seemingly jealous that Fuyuki hid this senpai’s existence from her, but Fuyuki instead is like ??? she’s just a normal upperclassman from school???
The scene switches and they’re on the way home. Fuyuki apologizes for not mentioning the senpai, but states that everybody has things they’re keeping from other people, and that’s okay. This, however, prompts Eri to reveal that she and Kyouhei have started dating. Eri apologizes, stating she only wanted to keep it a secret from Fuyuki to avoid hurting her, but Fuyuki takes this in stride. At the end of this chapter, Fuyuki apologizes in her head for keeping something else from Eri. It turns out that in high school, she had her first kiss with her senpai. It is implied both of them knew of their respective crushes on other people, and they decided to kiss each other out of comfort.
Chapter 4.1:
The chapter starts with Eri begging Fuyuki to hang out with her and Kyouhei the next day, but Fuyuki respectfully declines as she has a ton of homework to do, and she thinks that she should have some alone time with her new boyfriend. Eri is disgusted at Fuyuki referring to Kyouhei as her “boyfriend”. Fuyuki points out that the two of them haven’t hung out alone ever since they started dating, but Eri corrects her and says they probably haven’t hung out with each other alone ever since they started university. Eri then confesses that when she thinks about dating Kyouhei, something just doesn’t feel right, and then once again, asks Fuyuki to accompany her on the date.
The date itself rolls around, and out of habit, Eri pokes Kyouhei and calls him “Fuyuki” before remembering that she isn’t there. Eri then asks how long they have left until the movie and Kyouhei says about an hour and a half, but Eri grumbles wondering what they could even do until then. She scolds Kyouhei for not coming up with a plan and says that she likes it when she’s being escorted around on a date properly. Kyouhei admits that he didn’t come up with one out of fear that she would laugh at him, but Eri promises she would never laugh at somebody putting in an effort. Kyouhei is touched and promises that he’ll do it properly next time, but when Eri hears that there’ll be a “next time”, she finds herself deeply unsettled with that idea.
Meanwhile, Fuyuki notices that she’s out of treats for her dog, so she decides to go out and buy them, but strictly chooses to avoid taking a detour to the bookstore close to where Eri & Kyouhei are having their date. This is where chapter 4.1 ends.