So the sisters are doing lewd stuff to him because he's a harem manga protagonist (you know the type) and they find that weird. They're hoping that if he goes after them, Odin will be reincarnated. Worldly desires and stuff, I think. For a manga about Sakura Miyamoto being cute, we spend more time on the sisters than on Sakura Miyamoto. The sisters can combine into one being as well. Literally.
We don't get a full chapter on Sakura and her childhood friend until Chapter 4 of the LN (so maybe Chapter 5 in the manga?) But that chapter consists of her bringing up the usual childhood friend promise. After some fumbling around, MC also nonchalantly just tells her he loves her and asks if she loves him back. Cause he thinks she wouldn't realize if he didn't say it out loud. She stammers a lot because tsundere, but they start dating after that.
I feel like this would be better if we had a couple chapters on only Sakura and Ogami and their relationship first, then something like Chapter 4 of the LN happens, and then all of a sudden the three girls come in an interrupt claiming that he was a reincarnation of a Norse deity.