KOOLS-IFU is a low- to moderate-dispersion spectrograph in the optical range. It is unique because its integral field unit, with a bundle of 110 optical fibers, enables the acquisition of spectra at different positions of extended objects, such as galaxies, all at once. KOOLS-IFU is also used to reveal features of transient phenomena such as supernovae and stellar flares. We hope we report detections of the most exotic phenomena to us – gravitational-wave sources. Thus, KOOLS-IFU tells us the fourteen-billion-year story of the Universe.

TriCCS (Tricolor CMOS Camera and Spectrograph) is an optical imaging and spectroscopy unit that records photons simultaneity in three bands/channels. The detectors use CMOS sensors, which can capture up to 98 frames per second at the fastest speed, with the absolute time stamp obtained via GPS. While it can be used as a versatile instrument for regular imaging and spectroscopic observations, the instrument is designed to maximally contribute to time-domain astronomy by taking advantage of its unique time-resolving power and the telescope's large aperture.

GAOES-RV is an Echelle high-dispersion spectrograph designed to observe visible light with wavelengths around 500 nm. It achieves extremely high spectral resolution (approximately 65,000) while maintaining high efficiency using an optical fiber and an image slicer. Further enhancement is achieved through precise environmental control of the stabilized spectrometer and the use of an I2 cell containing iodine gas, enabling measurement precision at the level of distinguishing human walking speeds (approximately 1 meter per second) in velocity measurements. Developed with the aim of expanding the discovery capabilities to areas such as exoplanets orbiting more distant stars and lighter planets, it is expected to excel in a wide range of fields including planetary atmospheric chemical composition analysis, stellar activity analysis, and tracking of transient events.

This is an instrument for direct imaging observation of exoplanets. It consists of a coronagraph to remove stellar light and an adaptive optics system to reduce the influence of the Earth's atmosphere, which degrades its performance. The targets are nearby stars within about 10 pc of Earth. SEICA is expected to be able to detect gas giants such as Jupiter at distances of 0.2 arcsec (2 AU for a 10 pc star from the Earth) or further from the star. This instrument is designed to maximize the light-gathering and high-resolution capabilities of the Seimei Telescope.

Linear polarimetry instrument up to the wavelength of 1600 nm in the near infrared (NIR). NirPol and TriCCS are mounted in series, which allows simultaneous NIR and visual observations with them. High precision polarimetry is possible with the polarizing prism (in J and Hshort each band); it divides the incident infrared beam into two directions and then the two polarimetric images are obtained simultaneously (in each band). Examples of exciting studies includes 1) polarization of scattering from protoplanetary disks and 2) polarization due to interstellar extinction. Such a simultaneous imaging instrument of both linear polarization in the near infrared is rare (in the world), so unprecedented high-accuracy NIR polarimetry is very much expected.

This instrument has the capability to achieve simultaneous photometric spectroscopy of two targets in the near-infrared wavelength. By acquiring the spectra of a reference and a target simultaneously through two fiber bundle units, it enables long-term spectral monitoring even under the unstable atmospheric transparency of Japan's skies. The goal is to elucidate differences in the internal structure of active galactic nuclei located in the distant and nearby universe through spectral monitoring of them. It is a technically challenging instrument that utilizes world-first technology in its internal optical system.