You mean all harem animu copied Tenchi.
I raged at the ending too because the latter half was "Oh no! I'm not sure that I'm (one of) the girl(s) that Keitaro promised to go to ToDai although there was proof that I was there! I must run away!" and it felt vaguely copypasta'd.
I was sorta annoyed that Keitaro became a Seta clone and all the girls all of a sudden fell for him (and actually willing to take Keitaro away from Naru AFTER they got married which is sorta OOC for them based how they were throughout the series).
It should've ended with Keitaro and Naru getting together and Naru NOT being the girl that he promised to go to ToDai with.