The love story between Saito and Louise still has some remnants of that endearing dynamic between a really innocent and feisty adolescent and her loyal and caring companion who is also an adolescent but more mature, however this is ruined due to the constant barrage of sexual situations Saito finds himself in, where he either acts confused instead of stepping away or he directly cheats on her and then acts innocent... Which I kind of understand because Louise at this point has opened up about her feelings yet still refuses to be anything but extremely abusive and crazy. Either way that dynamic, which was one of the few good plot hooks is decimated for good here.
As far as the story goes, the anime has built a relatively interesting world, but all of it is only continuously used to generate new vulgar and sexual situations, so in the end the whole season is reduced to softcore porn, this season firmly established the harem formula. The OVA (ep 6.5) for a moment turns into tentacle hentai, and Tabitha's dragon ends up being sexualized as well (turns into a busty anime girl), a f*ing dragon, need I say more? Actually one more thing, ALL sexualized characters are underage, oh Japan...
The writing also isn't nearly as decent as in previous seasons, they straight up bring back a dead character with a very bs reason, in the end it just substracts from the low quality the anime already has.
I'll skip the final season, it was a huge trudge to just finish this one.
