Anime about sudden identity shift and past vs present self?

The title is a little vague and not entirely what I’m asking for so here’s some more details:

I want an anime where the protagonist (ideally male) becomes a version of themselves that’s different from the past in a sudden and jarring manner.

For example, in the disappearance of yuki nagato, nagato suddenly changes (like past halfway in the series) and describes her past self and memories as being asleep and awakening. She struggles in identifying what is her vs her past self, and when they start to mix (she describes as her past self waking up), she’s confused and doesn’t know what to feel or do. During the entire process, kyon is worried, but supportive of the current nagato, trying to help her through as her own person and not getting too caught up with the fact she’s different. Side character reactions (or more like deuteragonist interactions) are help elevate what I’m looking for. Ideally, it should mostly be feelings of concern, worry, and support for the protagonist.

Another example would be golden time which is… kind of the entire plot with Banri’s amnesia. So he doesn’t lose his personality midway through, it only changes during the end, but his past self is an influence to the plot and it is a shift between his past and present (only, the past version isn’t shown at all, different from nagato). I’d say the character interaction I’m looking for the most is with banri and linda. (Linda not making reference to the fact they have history and just trying to be supportive as a new friend) and also kind of the ending with koko where she tries to visit, but again just tries to acknowledge the current (I guess old in the context of this ending) Banri and despite her mixed feelings and distress, doesn’t try to fault or blame the current banri for it at all.

I know kanon 2006 might have something of this sort with its memory thing, but I’m currently watching and not that far in so I can’t say yet.

I also know that beyond the boundary has memory loss in the movie, with kuriyama struggling with rediscovering who she is/was, and I kind of like what the first half had, with the side characters trying to hide the truth for the sake of “supporting” or “protecting” the current kuriyama, but the second half about mental darkness kinda blows and that type of ending/message isn’t what I’m looking for.

Anyways, if you know of any shows with similarities to these examples, please let me know.