Kannagi

Only some though because there's obviously more than 50.

https://mynameismitchell.wordpress.com/2022/03/17/the-lineage-of-urusei-yatsura-the-romantic-invader/

It may look like a harem and smell like a harem, but it's not a true harem. Anime with harem elements that lack the qualifications of being full harem anime instead have harem subtext, the topic of this stack. This was partly inspired by the romantic subtext tag, but also the fact that there are many anime out there that may have harems in them, but aren't true harem series. This can often be because the protagonist simply chooses one girl early on and the rest of the 'harem' is left with unrequited love, or perhaps the protagonist has no feelings for any of the girls. Whatever the case may be, the story clearly does not treat enough of the girls as having a serious shot at the protagonist's heart for it to be a true harem series.

But what, you ask, makes something a harem series? Well, it's when at least three girls with importance to the story have a serious shot at winning over the protagonist. Harem subtext is when there may be several girls interested in the protagonist, but he doesn't return the majority of their feelings. Harem subtext can often edge into the love polygon/triangle theme, since while two girls may be interested in and have a serious shot at the protagonist, a third or more supporting characters may also hold feelings for him but they don't have a big enough role or shot at his heart for it to be a harem. Of course, girls simply existing around a protagonist does not automatically mean it's a harem series, even if it's a predominantly female cast.

Note that while some series may develop harem subtext later in their source material, if they do not have it in the first season then it does not qualify. It can qualify if the later material is adapted, though. Typically with these cases, a love triangle is already clear in the first season, but developments later in the source material turn it into a harem. Note also that some of these love triangles act like harems but with just two girls, where the protagonist is already in a quasi-relationship with both girls which they're aware of.

While this stack is focused mostly on harem anime and not reverse harem anime, I will include the latter if I feel it is warranted. I will be using the tag once per franchise, but do note that it can often fluctuate between entries, especially as characters are introduced and relationships develop. I will be using the first instance of harem subtext in a franchise, so if season 2 is the first instance of it then it will be included instead of season 1. Like the romantic subtext theme is with the romance genre, this stack is mutually exclusive with the harem theme, so if any of the entries here get updated with the harem tag, they will be removed from the stack. This also means that, as much as I hate to say it, I will not be including High School DxD Season 1. And yes, I will die on this hill.

In the following series, one or several cute girls suddenly start living with the protagonist, either in the first episode or soon after.
Hilarity and romantic feelings ensue, most of the time.