Because trees are immobile, they have evolved diverse traits to cope with biotic and abiotic stressors. Recent studies indicate that plants can communicate with neighbors via volatile organic compounds (VOCs), potentially priming anti-herbivore defenses in natural forests; however, field evidence and mechanisms remain unclear. We examined foliar condensed tannins and total phenolics in a mature Fagus crenata forest on Mt. Naeba, Niigata Prefecture, Japan (1100 m a.s.l.). All focal individuals were F. crenata and were assigned to three groups: (1) a putative VOC-emitting tree, (2) three putative VOC-receiving neighbors whose crowns were almost in contact with the emitter’s crown, and (3) three control trees located 30 m from the emitter and presumed to be outside its VOC influence. To mimic herbivory, we clipped half of approximately 90% of the emitter’s leaves shortly after leaf unfolding (7 June). Leaves were sampled on 8–9 June (1–2 days after clipping) and again on 1 July, 7 August, and 5 October (24, 61 and 121 days after clipping). Condensed tannin and total phenolics concentrations did not differ among the three groups at either sampling period. In contrast, both compounds increased across all individuals by 24 days after clipping, suggesting a seasonal rise in foliar defenses rather than a neighbor-specific priming effect. VOC profiles from the focal and neighboring trees are currently under chemical analysis, which will allow direct tests linking VOC emission/exposure to patterns of foliar defense in Fagus crenata forest.