I woke up and decided to read this way too early in the day and now I feel like I'm not going to get anything done with these two (and the TL notes/metro diagram) clogging up my brain.
The emotional seesaw of this chapter was something else - even within the same scene (two of them, even) there was a whiplash that really did feel like a bucket of ice water, which makes all that "cold" metaphor usage extremely apt. Though the first was much softer given Sumi-chan could turn to her Onee-sama for immediate confirmation and reassurance (shout out to Inner Macchi for pushing her to speak her mind), that second with the acquaintance from middle school almost made me think the chapter would spiral and end on a bad note.
Clearly I should know to have more faith, because their walk home was very much the insulating igloo in the blizzard.
I have a newfound appreciation for the complexity of quality translations of these stories, too - having to fight the multilayered ambiguity inherent in the Japanese language to find the best way to convey something as complex as their own multilayered relationship cannot be easy, but I think the effort has paid off here - because even with the far more sparse selection of words available for the English version, the poise, demeanor, and subtext alongside the illustrations do convey the meaning, to me.
Anyway, good chapter, best manga, fantastic TL, incredible notes page, would never want to ride that metro ever, but would follow this ship into eternity.