I've just read the chapter 42 as well... Basically... Friendship fic
Spoiler for Chap Summary:
Uiharu was feeling down, so Saten decided to take her out for fun, something about reaching the end of the rainbow- There was a really big Rainbow in the sky- Saten spoke of yet about 'urban' myth about finding happiness at the end of the rainbow. I'm assuming that Saten knows how rainbows actually work and that there's no such thing as the end of a rainbow
In the middle, we get a cameo of Fukiyose and Himegami, alot of creativity was put in to 'disguising' the latter's face for some reason
A few fluffy scenes later, the two girl climb up one of those super long flight of stairs up a hill to meet with the rest of Saten's friends. It's revealed that Uiharu was feeling down because a 'certain friend' of her was badly injured on a Judgement job because she didn't provide enough intel or something- Basically Uiharu blames herself for that person's injuries.
Then the rest is more fluff with Uiharu giving Saten one of her flowers to replace the hair accessory she had lost... Oh fun fact, when Saten asked about her flowers, Uiharu shot her down before she had even finished her sentence