Chara might be the more skilled and familiar with combat than Frisk, but when it comes to flirting they're nowhere near the master class Frisk is. Frisk might say that they're blushing, but it's Chara who's face is going beet red, despite trying to keep their smirk up.

"I guess, I-" they stammer a minute, trying to think up something to even say to that, hand rubbing futilely at their cheek as they try, and fail, to hid embarrassment. "I guess it's what has to be done! You go first, partner."