sworn elder brother; senior brother figure
Refers to a man treated as an older brother in a hierarchical, often non-blood, relationship, such as in yakuza or traditional craftsman circles. Contrasts with 弟分 (sworn younger brother).
See also: 弟分
older male partner in a homosexual relationship
Used in some contexts to refer to the older or more senior male partner in a male homosexual relationship. This usage is less common and may be considered dated or specific to certain subcultures.
He is looked up to as the sworn elder brother within the group.
In that circle, he is sometimes called the older partner.
Compound of 兄 (ani, 'older brother') and 分 (bun, 'part' or 'role'), literally meaning 'the role of an older brother'. The exact historical derivation is uncertain, but it likely emerged in Edo-period social structures.