Changed parents for everything from this pixiv post, because for some reason the artist appears to have taken the twitter uploads and recompressed them, so these are inferior duplicates. The filesize and quality level of the jpgs are much higher but all the same artifacts are visible.
Players are intended to watch Chapter 62 of the main story before watching the story for this card. I have not been following the main story, but from what I learned from other sources, I believe the events are connected to Haruka moving overseas, resulting in her leaving the main cast and Ortensia going on hiatus indefinitely. This is because her current voice actress at the time was about to retire. Basically, this is Haruka's farewell party.
The absolute tonal whiplash between this and the 4*s makes me laugh. It took the decimation of Mizuki's perception for Mafuyu to come out with the happiest card in a set.
The daisy she's holding is meant to look like an eye (you know, for the implication the song's singer ripped his eyes out). I'm adding the symbolism tag