Genos didn't know how his attraction towards his master--you, started.

It was originally his plan to meticulously observed your way of life. You're strong. Incredibly so. You’re the reason why he became your disciple. He wanted to know the very secrets you hid. Your way of life that led you to being able to accumulate force a strong enough to decimate possibly the world with one mere punch.

"Master, what should I make for dinner?"

Catering for you became like second nature to him. He'd thought of it normal, making you your favorite meals every day or doing the chores around the tightly cramped apartment that formerly housed you before he moved in. He had no problems doing whatever errands you had in store for the day, wanting you to be as comfortable as possible.

That wasn't the only thing either. With him being an S-class hero, he was constantly busy with missions and fighting off higher level monsters.

While he knows you're more than capable of fending for yourself, he can't help but worry.

There was a time where you once commented on how he acted much like a househusband would. Genos didn't comment. But the thought of it didn't upset him, either.

It feels nice, he thinks. You depending on him.

Somehow, it makes him feel needed knowing that he's in your life. A constant presence you've become used to.

He didn't think that Dr. Kuseno would program such emotions like love into his system. Or maybe, he’s been so blinded by revenge that he’d forgotten to feel affection for someone after his family was slaughtered unjustly by a rogue cyborg.