Dual Citizenship Question -US/Philippine passports (Manila)

I am a dual citizen - US/Philippines. I have two passports. However, my Philippine passport only has about 5 months before it expires.

I will be traveling to Japan from the Philippines in a couple of weeks using my US passport. Can someone please explain how I can go through the entry/exit procedures without getting into trouble with Immigration(i.e. losing my Philippine citizenship -- my greatest fear at this point).

(I know, I should've renewed my passport a long time ago! Haha huhu)