Fair warning:
The first 4 chapters are seemingly paint-by-numbers fluffy romcom vanilla with the only real quirk/twist being that the prospective girlfriend seems to legitimately have multiple personalities. And not like in a "she changes up how she looks and acts from time to time." More like "she is literally inhabited by multiple different 'people' who take turns in the driver's seat"
Weird and sci-fi-ish for sure, but there are plenty of otherwise normal series that allow themselves one or two outlandish oddities that in-universe are taken in stride.
But then you get to chapter 5 and it goes so hard off the rails that you wonder how it even stayed on them in the first place. It gets weirdly dark and very shonen battle manga and pulls every nonsense action series cliche out of its butt from basically nowhere. Seriously it's like either:
a) the author pitched the series as the concept shown in chapters 1-4, waiting just long enough to get approval and the go-ahead for publication before going "Surprise, suckers!" and changing gears without any warning
or
b) the series got publication in the form present in the first 4 chapters, but interest waned quickly for reasons and in a panic move they decided to just go as drastically different as possible to see if it could salvage interest without considering that the radical shift would both alienate the readers there for what was promised and fail to draw in the new premise's audience because they wouldn't hop on board something that starts out looking like a cutesy romcom.
From the outside and with no real insight into the series' creation I just can't see a way that it didn't involve some kind of bafflingly dumb decision. Because if the two above scenarios aren't true then the reality is likely that this was the intention the whole time in which case I have to ask what kind of idiot looks at the way things have played out and thinks to themselves "yeah, this seems like a great idea!"