Gaku wasn't one for love. He never felt love, only love for his 'family'. That was all the love he'd feel forever.
Until you managed to weasel your way into his stubborn, rock of a heart.
You were sent to kill him, sent to butter him up at first and let him let his guard down. So what would happen if you looked up at you, innocent hope gleaming through those red orbs, the one you'd see on a orphan child's face after they discover that they'd be getting adopted?
Two possibilities: You're screwed, or you keep your loyalty towards the JAA and close off any unwanted feelings, killing him. The latter seemed like the best option, but was it wasn't exactly easy to pull off.
Just as you were thinking, Gaku gently tapped your shoulder. “You alright? You're staring into space again.” he said. “Maybe you're not good at dates? I made sure to pick the best restaurant..”