All over her face and tits.

Negi: I don't want you to get pregnant...so, i...i'd like to cum on your chest!!

Makie: Mmmm, good thinking, Negi-kun! Ready!?

Negi: Yes!!

Makie climbed off him and gave his cock three long sucks before taking it out, jacking it fast and aiming it at herself.

Makie: Yeah! Cum for me, Negi-kun! Cum all over my boobs!!

Negi arched his back as he started firing squirt after powerful squirt on to Makie's tits and face.

At the same time.

?: Negi-sensei, i forgot my book-YAAAAAHHH!!!! M-m-m-m-m-m-m-m-m-makie!!!

Negi: N-n-n-n-NODOKA!?!?!

Makie: Mmmm...Negi-kun. Huh? DWAH!?