Looking at one of the screenshots for Madou Monogatari 1-2-3 (PC-98), I noticed a spelling concern.
Stop should be extended by extending the consonant, not the vowel. For example, here's a huge difference between ohh (an elongated oh, as in "Ohh... I see...") and ooh (as in "Ooh, I like it!"). Also, just in case, I might as well point out the difference between ahh (an extended ah, as in "Ahh... I see...") and aah (as in "Aah! A Spider!"), as well as uhg (as in uh + g) and ugh (as in the GH makes a voiceless velar fricative sound, also used in the word blegh, also sometimes spelt Scottish/German-style as "blech").
"Stoppp!" would certainly be better.