Actually, you're being unbelievably idiotic and biased, meaning you're either fucking stupid, or a troll. I'll humor you and assume you're the former.
He mistook the situation as him being rewarded with a kiss. A foreign man in a foreign country, being commanded to kiss a beautiful girl? Yeah, what a cheating bastard, Saito is! And where's him chasing the other girls then? As I said, he stares at tits, but that's about as far as it goes. Siesta made up lies, and Henrietta jumped him. He snuck into the wrong bedroom trying to FIND Louise to tell her how he felt, and wound up in her sister's room.. so far, I don't see him going out of his way to cheat. Hmm. Could it be that you're simply full of shit? Only one way to find out - let's continue!
Del actually told her to outright SAY "I love you, Saito!" His specific advice, that. But no, she fussed and whined and refused to do that, and so Del came up with Plan B, which was the catsuit. Again, my point is proven - the bitch refused to fess up.
Even when asking him to marry her, she never told him 'I love you'. What'd she do? "It's just that I don't want to die before getting married!" is what she did. Still not seeing her go the distance and just telling him how she feels here. Looks like you're just full of shit after all. Go rewatch Season Two, ya biased cunt.