This collection of papers explores Japanese mood and modality from the perspective of Systemic Functional Linguistics. It aims to enrich the general discussion of language, function, and cultural connotation, while also offering a cross-linguistic and interdisciplinary exploration of modality. The collection contains five chapters, each focusing on different aspects and dimensions of Japanese mood and modality. The chapters cover the system of Japanese modulation, contrastive studies between Japanese and English interpersonal metaphors, a comparison of the modality systems of English and Japanese, and the cognitive and linguistic reasoning process of the speaker's choice of modal expressions. Overall, the collection offers a well-elaborated exploration of the interpersonal metafunction of the Japanese language, providing insights into language forms and cultural implications.