In this talk, I will outline our recent research activity on the rest-frame spectra of quasars at 4.5 < z < 6.5, and introduce our recently approved research program to study the evolution of quasars and galaxies beyond the currently explored parameter spaces. The first part of the talk will concentrate on the study of quasars at 4.5 < z < 6.5 using AKARI. Taking advantaged of the AKARI's unique spectroscopic capability at 2.5 - 5.0 micron, we have obtained the rest-frame optical spectra of quasars at z > 4.5 for the first time. We will discuss our result and its implication to the grown of the supermassive black holes mass. In the second part of my talk, I will outline our research program approved by the Korea Science and Technology Foundation, which aims to study the formation and the evolution of galaxies and quasars through NIR-optimized wide-field survey. Such an effort needs the use of a 2-m class telescope capable of wide-field imaging, such as the Du Pont 2.5m, and possibilities for collaborative activities will be discussed.