TLDR:
>MC (Taiki) is away on a school trip for a while
>FMC (Chinatsu) is living alone for the first time
>New unknown neighbor dude shows up immediately with expensive gift at night when she is alone

In chapter 199, Chinatsu’s new neighbor rang her doorbell late at night just to give her a housewarming gift. And as we see, they brought a whole box of Ukokkei Baumkuchen. I looked it up, and a box of Ukokkei Baumkuchen costs 5,281 yen—which is pretty expensive for a housewarming gift
https://www.ukokkei.co.jp/c/21

If you're not familiar with Japanese customs around housewarming gifts for new neighbors, here's some data I found on a Japanese site:
https://hikkoshizamurai.jp/report/report015/
>Typical Price Range and Popular Items for Housewarming Gifts
>The total amount spent on housewarming gifts is most commonly under 1,000 yen.
>Many people choose to give small, token gifts, and the lowest per-household amount recorded was 200 yen for some detergent.
>Even from the recipient's perspective, expensive items can be difficult to accept, so it's better to keep the gift modest.

Chinatsu’s new neighbor giving her an expensive box of Baumkuchen is already kinda weird, but what’s even weirder is that they chose to give it to her late at night. Couldn’t they have done it during the day like a normal person? It just feels like they completely lack common sense. If I were Chinatsu, I’d definitely be weirded out.

I checked out the reactions from Japanese fans, and they also think it was strange. This sudden development made a lot of people uneasy.

https://togetter.com/li/2564813

Chapter 200 spoiler:
When they arrive at the inn, Taiki calls Chinatsu.
She’s her usual cheerful self.
They switch to video call so they can see each other as they talk.
Chinatsu is in the middle of eating that baumkuchen she received earlier.
She just says it was a gift — but there's still no clue shown about who it was from.