Will no Dengon

Heroine Lucia lives in a peaceful town of "Will". She hears from boy Rui who she helped in the forest that the neighboring town Wolfe is going to attack. There was a legend that once per 400 years a demon comes down to Will and Wolfe intended to utilize his power. To stop the assault Lucia is preparing to attack the front base of Wolfe on an aircraft.

[From vndbreview]