This one got me conflicted, smut but good...
MC got reincarnated into some crossover world where the base is MHA, so far there is MHA, DXD, Nisekoi and MCU. He has the body and mind of Adam from Record of Ragnarok and some very convenient powers as well as the best thing of the novel, A system that allows him to summon waifus to the world for the uncultured.
Writing Quality: Good, nigh-perfect English, the only thing I complain about is delivery.
Stability of Updates: Can't say much here as I sadly caught up in a Hiatus, hope it is not dropped.
Story Development: Very well done plot for a Smut novel that usually doesn't have fk all.
Character Design: Great character design, the girls are very loyal to their original personalities.
World Background: Many interesting locations however proper scenario description is lacking in most scenes (Characters' position, weather, furniture etc...)
Now comes my personal opinion and I shall judge it in a Smut POV.
I like the development of the relationships with the girls but you make a lot of sexual tension between to make a very average lemon scene. Usually, it is the other way around, authors make great lemons but leave the development aside.
MC barely shows emotions, there are too few dialogues in some occasions where the scene could've been more meaningful, for example, Tsunade and Rias' scenes however I can't really blame you for that since the whole thing is Smut.
Sadly, the girls are treated as objects to some extent, they don't have any life aside from Fking MC and watching TV except for a few ones. Sometimes the harem is so big that some girls aren't recalled often.
I love the diversity in the harem, every single character is a remarkable woman/girl.
In my humble opinion, I believe you should continue developing the girl's characters but more in a spiritual way. Make them useful, give them occupations, that way you don't have to put all of them on a screen all the time.
The girls are literally fked silly, and none of them is a weakling, and even if they were somehow ambushed, MC can protect them with the help of the system. So why not make them go their way and involve them in that world's society?
Some of them could work part-time in stores (mikasa, ning'er, meiko, yumeko, eve, kurumi, marika etc...), some of them could be teachers (Vados, LD, Grayfia, Gray) some of them could be trainers (Tsunade, Albedo) some could be office workers (Mamako, Raikou, Mitsuki), or they could be maids, Natasha can keep working as a spy there are a lot of scenarios that you could use not only to make smut but also to develop the relationships with the girls other than just fking. Rias should still have her peerage
Come on man you have a crossover with worlds that don't lack events and possibilities, you can do better.
Greetings.