Dude that's so heavy. I figured Aqua had some feelings for Kana, but damn. He's right though. He's Prioritizing her safety, and her future. Comes above all else. His statement is unmistakable. If he could he would date her. The possibility that his real father, co would target Kana to get at Aqua is very quite real, or what happened to Ai by some stalker is highly probable. There's a few scenes in the manga, and anime where Aqua was looking at Kana in a romantic way. Where he noticed her for the first time.