As a candidate for latent heat storage materials, a semiclathrate hydrate (SCH, a kind of clathrate hydrate) has been expected. A remaining challenge toward the practical use of SCHs is to diminish a large degree of supercooling in the SCH crystallization. One of the effective solutions is the utilization of the hysteresis called the “memory effect”. The memory effect diminishes supercooling and/or the induction period in the clathrate hydrate recrystallization. We have elucidated that the solution structures (called clusters) remaining in the aqueous solution after complete SCH decomposition is closely related to the memory effect. In this paper, we introduce the experimental results on the residual clusters in the tetra-n-butylammonium bromide (TBAB) aqueous solution resulting from TBAB SCH decomposition, which were observed by scanning electron microscopy (SEM) with the freeze-fracture replica method, a small-angle X-ray scattering (SAXS), and a high-precision differential scanning calorimetry (μDSC).