1. As the main character, he's the most normal person on the show... Despite his own abnormalities.

Daria is a "brain," which is 90s for "geek" or otherwise "unpopular," so in a way she's not normal, and yet she's the most trustworth and sane character in the show. Then we have Saiki... Just look at him, pink hair, antennae? Not to mention his, well, very abnormal psychic powers. Still, he's the most sane character compared to the rest of the colorful past.

2. Both have a dry/deadpan sense of humor

Daria's way of making it through high school life are her sarcastic remarks and aggressively realistic outlook on life. Saiki's life is anything but normal, but her uses his powers for mostly pragmatic reasons. Not to mention his not smiling unless he has a reason (Even if it's just coffee jelly) frequent utterances of "yare yare," meaning "good grief" or "what a pain."

3. He's surrounded by a colorful cast of characters

Of course, despite Daria just wanting to make it through high school, she's surrounded by a good amount of people who give her trouble. Of course, in Saiki's case, as in most animes, he can't avoid it either with the foolish Nendou, the Hero Complex Kaido, and the "Perfect Pretty Girl" Teruhashi just to name a few.

4. He still cares

Daria doesn't seem to care too much for her friends or even her family, but in the end she shows she truly does. She gives advice to her superficial sister, and does her best for her wacky parents and classmates. Saiki of course even says he doesn't care, or that his friends aren't really his friends, but ends up helping them, usually with his powers.

He points out social flaws

Of course one of the biggest themes of Daria are the "outcasts" seeming more human, along with Daria making long speeches about why society sucks with the imaginary camera zooming in. Saiki does this as well, but in a different way. He does make fun of all the crap that goes on in anime by saying that he's responsible for it, but he also points out the everyday, like high school romance, popularity, even pets.