About the side marriage thing I don't know if it's added yet and if it is can someone tell me how do it because I've searched mostly all places renryuu ascension was uploaded and couldn't find any information about how to do it and neither was it in the walkthrough 

It's added. You can marry mai and dea both. And it's in the walkthrough as well. Basically you just need to complete all their quests and open all scenes before marriage