Toujou Basara has a very intense father in Shinmai Maou no Testament. Basara has always been an only child and his father always single, but it looks like things are about to change. Suddenly, his father announces that he will be getting remarried, but to a woman overseas that already has two daughters. The catch? The daughters are coming to live with Basara! And the even bigger catch? It turns out one of them is a demon-Lord-to-be, and the other is actually a succubus. Basara may have wanted a little sister his whole life, but this definitely wasn't what he had in mind…

Like Monster Musume no Iru Nichijou, the lead boy of Shinmai Maou no Testament finds himself left without any parents to fend for himself alone - or well, almost alone. Of course, he is joined by the monster girls! Kimihito may have a whole harem of them living with him, but the two that Basara has to deal with cause him more than enough trouble as it is. With one being a demon Lord and the other a succubus, Shinmai Maou no Testament is great for fans of darker supernatural girls especially.

Both anime have great ecchi sequences in them as well with the supernatural girls and the human boy. If you liked Monster Musume no Iru Nichijou, and especially if you like the brother/step-sister trope in anime, Shinmai Maou no Testament is a great follow-up anime to enjoy. It's darker and more action-oriented, but the ecchi harem idea has a very similar feeling.

Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka (here on out referred to as “DanMachi”) is a fantasy anime set in the fictional town of Orario. In the centre of the town is a strange dungeon full of all level of beasts and baddies – and of course, plenty of treasure and experience for the taking! Thus, Orario is full of adventurers and all manner of merchants and assistants that go alongside them, along with many gods and goddesses that sponsor and support their teams of adventurers who fight in their names. Bell Cranel is one such adventurer, a young boy just looking to become a true warrior and make a name for himself despite not being part of a fancy guild, and being supported only by the small goddess Hestia who has no other adventurer but him.

DanMachi is based on an otome game with many different routes for the main character to take, which is the perfect setup for a harem anime. And it takes full advantage of that. Combine it with a fantasy setting full of girls of countless species from elves to goddesses to girls with fox ears and everything in between and you've got DanMachi.

Much like Kimihito, Bell is a younger boy that finds himself surrounded by these women without really knowing how to handle it appropriately. They both go through crushes, jealousy, and fights with their wide array of fantasy girls, learning a lot about relationships (both friendship and more) along the way. Kimihito lives with many of the girls, and Bell lives with just Hestia, but the fun and fanservice are always guaranteed to follow our main character home in both anime.

Both DanMachi and Monster Musume no Iru Nichijou are fun and light-hearted fantasy harem stories that are easy to watch. They complement one another without making you feel like you're just watching the same anime again.

Mamori Tokonome starts off Valkyrie Drive: Mermaid, unfortunately, kidnapped from gym class and transported to an exotic and scandalous island called Mermaid. Mermaid is far from a relaxing, tropical getaway, however – in fact, it’s full of many enemies and predators! Luckily for Mamori, she is soon discovered by Mirei Shikishima, who teaches her that through passionate kissing they can unleash special transformative powers to fight against these enemies. The more aroused they are, the more powerful they can fight, and they are going to have to work together if they ever want to survive their time on Mermaid.

Valkyrie Drive: Mermaid is a shoujo-ai, so the romance that happens is between girls instead of a boy and a girl. Thus the harem of girls in the story is clearly going to be interacting with a heroine rather than a hero. But it's still a harem of fantasy girls revolving around one (mostly normal) human, just like Monster Musume no Iru Nichijou. The romance in Valkyrie Drive: Mermaid mostly centres around Mamori and Mirei themselves, but there are many other girls that they encounter along the way as well on Mermaid Island. And throughout the story, the romance sequences themselves highlight Mamori's newly discovered magic powers. She can't activate them without passion after all, which makes romance very important to the story.

With all the different kinds of girls in Monster Musume no Iru Nichijou, the fantasy element of their romance stories is always highlighted as well by all their unique supernatural quirks and features. Both anime keep that fantasy and magic kind of romance at the centre of the plot, so if that is what you like, check out Valkyrie Drive: Mermaid!