Secretly More Powerful than the Hero

Story:

From a young age, I've always dreamed of being that “unassuming hero,” appearing ordinary but possessing unmatched strength. But one day, fate took a turn when I was hit by an eight-ton truck, and suddenly, reincarnation was on the table! "What would you like to be in your next life?" asked the goddess of reincarnation. Eagerly, I replied, "I wish to become a wimp, but secretly OP!” She granted my wish, but with an unexpected twist: if anyone ever uncovers my true abilities, my heart will explode! This isn't quite the “secretly-OP-wimp-life” I had in mind…