He admired her skill.
Regrettably, maybe, because as a scientist he often refused to acknowledge the existence of magic (it wasn't logical, where did magic even come from? How did it work? He could never wrap his head around it), but he admired her skill as a magician greatly. He found it useful, even, he thought maybe time and space magic was just what he was missing to successfully return to his past, in the correct timeline.
However, the Dimension Witch wasn't so quick to devolve her secrets of bending and manipulating time and space and reality itself – much to his dismay.
She would tease him about it, despite knowing how violent he would get (sometimes it resulted to her having to teleport herself back into their timeline, which sometimes didn't work out all too well), all because she enjoyed seeing the Diabolic Esper become flustered. Eventually, he would just pout and fold his arms, plopping down on the floor almost like a baby. She would laugh and plop down in his lap, throwing her arms around his shoulders and pressing a chaste kiss to his pouty lips.
Add put up with this, not just because he wanted to know the secrets behind her magical abilities, but because he really did love her, even if he stubbornly refused to admit to so. Something about Aisha's bright smile and teasing nature brightened his day – even if he couldn't quite put his finger on it.
So, day by day, he would continue to put up with her, and she would continue to tease him. All for the sake of discovering the secret to her power, right?
Or at least that's what he would tell himself.