A bit of energy

Natsu could feel two things during this handjob.

First was his cock slowly building up, getting ready to burst.

And second was his magic energy slowly draining.

As he looked down at the naked blonde jerking him off, he tried his hardest both to keep his cum and his energy in.

But eventually, his efforts failed. His load cascaded over Lucy's tits and arm.

She smiled and stood up.

"How was that, Master Natsu?"

Natsu panted, recovering his stamina...

"Lets see... Summoning you took like 2%. Seems like I lose another percent for every hour you're here... And that handjob... It was something you apparently really didn't wanna do normally. So I lost like 20%."

He was down to about 77%, then.