Maybe, but you still can follow the line of how it went.
we already knew that Uki was the little sister of her big bro (I don't remember his name) and that they went to the same class, so there was the doubt of how she hid her kappa characteristics if her twin brother didn't, so the mangaka started with a focus on the brother and quickly answered the question, it added a bit of world building with the water spear part, made some foreshadowing with the sisters part,and ended showing how mizudako used her powers by accident because she wanted male lead's attention
Putting a good ammount of focus on secondary characters is what makes or breaks these types of less serious romance manga. If you just focus on the main couple, the manga starts feeling slow and padded out by the second volume.
I just find it hilarious that someone with the PFP of the Ancestor, aka Local Man Ruins Everything, from Darkest Dungeon, is commenting on Anime Highschool Cthulu girl.