On Terrace House there is a word that is often translated as "really?" or "seriously?" It isn't hontoni, but something that sounds like "maji".
So for example a character tells another that, surprise, he's made bentos for the two of them. She says "maji de?" which is translated as "Did you really make lunch?"—I know this isn't an exact translation.
Second example, a guy says he's going to eat ramen late at night and someone responds, "Ramen? Maji?" This is translated as "For real?"