@monkey123
I think when he said he was going to go all out he decided to go ahead and do some ecchi things to her. Things that may reset but leave a lasting memory.
Or it could have been like another said and he used a crazy attack and scared her enough leaving the fear even after the reset. Given previous actions personally Im betting he went the sexy route.
And I dont remember, is this based off of a novel? Anyway, I imagine it is going to be explained or shown at some point, unless it is a 'novel exclusive' scene, as happens in some other series.