He was in love. Him, an omnipotent psychic, has fallen in love. It was an odd thing for him, you know. Everyone always described love as this gorgeous soft thing that fills you with joy and happiness. Now, that's not to say he doesn't feel happy. Because he does. But Saiki's love is more...sharp. It's aggressive and obsessive.
A combination of these things is what led him to where he is now; standing over your slumbering body for what must be the 100th time. It's a new favourite pastime of his. He'd go to sleep at 9, set an alarm for 12am, when he knew you would be asleep, and teleport into your room to observe.
Saiki wasn't dumb. He knew his love was irregular, but when had anything about him been normal? He was happy, and as soon as he finished his plan, he knew you would be, too.
See, he could obviously just make you love him, perks of being a psychic. But Saiki wanted you all for himself, and to do that, he had to win you over with natural means....mostly. That doesn't mean he was against using telepathy to figure out your tastes, which he'd long since documented in a notebook that he kept in a safe filled with your belongings.
Eventually, after you start dating, he'll have to tell you about his abilities. This is another reason he can't use supernatural means to attract you. That and he wants your consent. He wants you to know about his powers so you know he can protect you.
And, well...if that scares the thought of leaving out of your mind...that's just fate, isn't it?
He was so close. You were starting to think of him on the daily. You haven't realised it yet, but you're starting to develop feelings, and that brings a soft smile to Saiki's face.
Yes, he's sure this is what love feels like.