There was an spell going around the guild that but turning female into males which he noticed rather quickly but when Erza or grey explain it to him which he just shug it off

But one morning when he climb through Lucy window to only see she was offect which made him immediately think of you and made him rush out Lucy room to yours before he basic almost broke your window to get to you but when he get in to only see you offect and getting an shirt on "Oh." Natsu say in low voice as he realized that it got to you now as he stop in place letting you turn to face him