Let's talk about this in two sections.
SECTION #1 consists of chapters one through let's say about chapter fifteen. It tells the story of Sansui who transmigrated to a fantasy world and then trained as a sage for five hundred years, developing overwhelmingly strong yet boring sword skills. Fe can defeat anyone in one or two strokes of feir sword. Upon finding a baby in the forest, feir master sends fem out of their hermitage to raise the child in human society. Fe gets a job as a bodyguard for the daughter of a noble family and fe lives a laidback life, defeating any threats and challengers with the utmost ease. It's cute.
SECTION #2 starts around chapter sixteen and is currently ongoing. It tells the story of the kingdoms of Arcana and Domino and their various power dynamics. In Arcana, there are the four noble houses--Sopeid, Batreble, Caputo, and Discia--and each of these houses has its own "trump card." Sansui is the trump card for house Sopeid. The fact that each noble family has its own transmigrated Japanese person with cheat-level abilities is nice and symmetrical and all, but it really makes the fact that Sansui joined femself to Dewey feel much less spontaneous. It makes the entire story feel too orderly and fated. This section of the story also includes an emphasis on the eight Divine Treasures, and we are introduced to six of them. Four of them are in the control of the neighboring country Domino. Again, this emphasis on having things fit into orderly boxes is not great. The main failing of this section, however, is that it tries to take a lighthearted and empty story and give it seriousness. We already know that Sansui's going to defeat whoever fe comes up against, and easily, so there will never be a sense of tension. The only reason why feir overpoweredness was at all acceptable and fun to read was because the manga didn't try to force that tension on feir battles. Now that it is trying to make feir fights have actual stakes, it still lacks any tension so it ultimately fails, and it's nowhere near as interesting to read.
[Reviewed at chapter 31]