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Asteroids are believed to have the so-called "rubble-pile" structure (i.e., gravitational aggregates) and several evidences point to this kind of loose interior structure, including (a) smaller bulk density smaller compared to the composition materials, (b) asteroid families, (c) boulders on asteroid surface, and (d) the 2-hr spin-rate limit. However, the rubble-pile structure has been challenged recently by the discovery of super-fast rotators (SFRs), a group of asteroids supposed to be destroyed by a spinning of < 2 hr (i.e., centrifugal force > self gravity). In order to understand SFRs itself and asteroid interior structure, I used wide-field telescopes (e.g., PTF, ZTF, PS1, and Subaru/HSC) to collect numerous asteroid light curves and tried to find and study SFRs. In addition to asteroids, I also try to find the spin-rate limits for Hildas and Jupiter Trojans. This helps to understand if the rubble-pile structure can be applied to other asteroid populations as well.