Youkai Apartment no Yuuga na Nichijou

Can't have a series about humans and youkai interacting without mentioning the granddaddy of them all. Both protagonists deal with issues of isolation, the death of their parents and finding one's self. Both are surprisingly heartfelt in places but mix in a good dose of comedy as well. 

These are both slice of life shows about youkai, and masters who can control them. They are both pretty relaxing. Youkai Apartment has more comedy elements than Natsume Yuujinchou. 

What if humans could interact with supernatural beings? These two anime will answer to that question, in two different yet similar ways. Both in Natsume Yuujinchou and Elegant Youkai Apartment Life develop their protagonists to learn how to live with the youkai in their lives. Although story wise it isn't completely alike, it does share similar traits. 

Both Natsume Takashi and Inaba Yūshi are orphans that had trouble fitting in with other people (whether those people be classmates or living relatives), and they both have an affinity with yōkai. Although they are both friendly with yōkai, they are both close friends with an exorcist. Both Natsume and Inaba find themselves in the possession of a magic book (Inaba's book chose him, and Natsume's belonged to his grandma). Both Natsume and Inaba try to keep their book and connection with yōkai a secret from their human friends (Natsume because he was bullied as a child for his ability to see yōkai, and Inaba because he wouldn't believe it himself if it wasn't happening to him). read more 

Both supernatural anime's centering around a boy who is able to see youkai. Circumstances are different in both but their interactions and making friends with them are similar to each other. They both have fun moments and serious moments balanced in with the two but are generally a good time to be had. You can expect to also see a few casts of attractive looking male characters in both too. 

A reluctant protagonist dropped into the world of youkai, exorcists, and the supernatural and ends up deeply appreciating the situation...growing from it. High school setting. Interesting characters and overall design. Excellent background detail. 

Another series focused on the relationship between youkais and humans, with more action in Nurarihyon no Mago. 

The same situation where guy gets into an apartment full of supernatural beings where he finds himself being able to fit in.