dark clothes guy: "キツイ.. もう.." Hard.. already... = frustration and tired that this girl is dead fish so whatever he did didn't make her more horny. light clothes guy: "オイ! がんばれ!!" hey! keep do your best!! = Dude! don't give up!
Miniguys trying to find the G-spot from the inside is even more difficult than finding a needle in a haystack because at least you know what a needle generally looks like.