We constructed a catalog of volcanic deep low-frequency (DLF) earthquakes across 52 regions in Japan to investigate their seismicity based on three analyses: relocation, classification, and detection. Relocation and classification analyses are based on waveform correlation, and detection analysis is conducted using the matched filter technique. We found that DLF earthquakes in many regions are spatially clustered at approximately 5 km intervals between the lower limit of crustal earthquakes and Moho discontinuity. Based on temporal seismicity patterns, DLF earthquake groups in each region can be classified into episodic and non-episodic types. Episodic groups consist of seismic swarms and quiescence. In some episodic groups, DLF earthquakes have constant recurrence interevent times or increasing interevent times as a function of time. Swarms of DLF earthquakes sometimes are associated with volcanic activity at the surface, such as eruptions or crustal deformations in some regions. The spatiotemporal characteristics of DLF earthquake groups may be linked to the movement of magmatic fluids. The discrete vertical separation of DLF earthquake groups may reflect small-scale heterogeneities, such as injected magma. Periodic activity patterns may be caused by volcanic mechanisms, such as second boiling. The variety of DLF earthquake patterns may suggest that multiple mechanisms may trigger DLF earthquakes, such as complex underground structures and volcanic processes, rather than a single mechanism.