This is Chapter 14 in Volume 3 of A Place Further Than the Universe
The caravan of snowcats sets out, headed for the inland research station. As they sleep through a blizzard, Kimari thanks Shirase for bringing her. Shirase sends one last email to her mother, before they arrive where her mother is. Upon arrival at the station, where the expedition intends to build an observatory, Kimari remembers Shirase's comment, "If I go there and nothing changes, then I'll keep on feeling this way for the rest of my life". Kimari dashes off into the station, desperate to find a memento of Shirase's mother. She finds Takako's laptop computer. When Shirase boots it up, all of the unread e-mails begin to load; the ones which she has been seen writing in every chapter up to now. She cries out for her mother, and they all break down in tears.
This chapter is based on Episode 12 of the anime.