You use the last flickers of magical energy you've got left as you reinforce your legs. Arcueid might massively out-speed you even now, but you're close enough that the distance between you and Morgan can be covered quicker than the distance between Arcueid and Morgan! Of course, this is only possible thanks to Arcueid seemingly not going as quick as she possibly can, but even so, her speed is beyond a human!

Part 18