the main event of volumes 2 and 3 specifically was the summer festival where they watched the fireworks and Konatsu felt hurt for the first time by being unable to fully understand and communicate with Koyuki.
I re-read those two volumes and this was basically the biggest thing I noticed. The majority was the two of them getting closer, but essentially not close enough:
https://dynasty-scans.com/chapters/nettaigyo_wa_yuki_ni_kogareru_ch11#23
https://dynasty-scans.com/chapters/nettaigyo_wa_yuki_ni_kogareru_ch11#24
(she's referring to the fireworks festival)
There's also Konatsu going on about how much she likes Honami, but in the same chapter, she realizes that they still are emotionally distant with one another
https://dynasty-scans.com/chapters/nettaigyo_wa_yuki_ni_kogareru_ch11#13
Here's Konatsu fangirling for a few panels.
This could be attributed to the fact that Koyuki is the first person that she's allowed herself to get close too, so she most likely isn't used to how close a friendship is; to her, Just talking to Honami on the beach was enough for her to call her a friend in Ch 1, but at the same time, she acknowledges that there's so much more in a friendship than talking and being comfortable around another person. Konatsu seems to have a surface level understanding of friendship, and maybe next chapter we will see some more growth there (although the past 5 chapters have been all growth)
On Honami's end, she's almost the complete opposite. Although she was in the same situation of loneliness and isolation as Konatsu, while Konatsu's loneliness (regarding friendships) came from her own actions (Her constantly concerned with "fitting in" and not telling her classmates that she was leaving, not being on a first name basis with anyone at her old school) Koyuki's loneliness comes from how others treat her (She wants to be herself, but feels like she can't in contrast to choosing not to). In volumes 2 and 3 Honami exerts possessiveness and jealousy in her interactions with Konatsu (literally the plot of chapter 7 was Honami feeling depressed over Konatsu allegedly choosing Kaede over her to go to the festival with). In chapter 10, what used to be her daily routine seems unbearable without Konatsu. In Honami's case, she seems to just want more and more of Konatsu (something that never really goes away).
Maybe in the next chapter will see the fireworks festival addressed, along with them discussing the actual nature of their relationship,, something highly probable as they can compare their closeness with the closeness of their mutual friend/shipper, Kaede.
Man, I usually save these long analysis for after a chapter comes out, but I just couldn't help myself.