Love is a powerful emotion, bringing with it the need to protect. Some might even call them identical, for if you love something you protect it, and why protect something if not love?
Watari has that protectiveness in droves, yet if asked, would profess no love save science.
If asked. Love does not need to be admitted, or even realized, to exist, and to instill protectiveness. In truth, Watari loves everyone.
Tsuzuki, Hisoka, Wakaba, Terazuma. Tatsumi. Even Kanoe and the Gushoshin, in the simplest way possible. He protects them, he heals them, he cares for them.
What else is love?