"Seishun Butayarou wa Orusuban Imouto no Yume wo Minai" (rascal does not dream of house sitting sister) by Kamoshida Hajime. This is volume 5 of the series, featuring return of the original sister.
The current Kaede up to first half of this volume does not have any memory of the past, everything about her is different from the original including being right-handed as opposed to left-handed. The loss of memory caused conflict between Kaede and her mother, which explains why Sakuta and Kaede lives away from their parents. The loss of memory also explains why Kaede did not recognize Mai as a celebrity.
After finally appreciating Kaede's background, the second half of this volume proceeds to slowly replace the current Kaede with the original. This was a clever move by the author to get the readers to really like a character, and then take that personality away without just killing them off. For all the hints that were planted from the very beginning about Kaede's very memory loss, and then getting everyone to feel a sense of loss despite what should have been a return to normality -- the author was definitely planning far ahead, and this plan was well executed.
This volume covers the end of the TV series up to episode 13. Actually episode 13 includes a little bit of volume 6, but excludes the final confrontation between Shouko and Mai. That last scene leads to the scenario that is the real heart of this series, to be continued in the next volume.
Previous (2019-08-30): "Seishun Butayarou wa Siscon Idol no Yume wo Minai" by Kamoshida Hajime
Next (2019-10-04): "Seishun Butayarou wa Yumemiru Shoujo no Yume wo Minai" by Kamoshida Hajime