noun
co-debtor; joint obligor
Legal term for a person who shares a debt or obligation with others. Used in contexts such as loan agreements, guarantees, and joint liabilities.
共同義務者として、彼も借金の返済責任を負う。
As a co-debtor, he also bears responsibility for repaying the debt.
連帯債務者 refers specifically to a joint and several debtor, where each debtor is liable for the entire obligation. 共同義務者 is a broader term for any co-obligor, not necessarily with joint and several liability.
Compound of 共同 (kyōdō, 'joint, common') + 義務 (gimu, 'duty, obligation') + 者 (sha, 'person'). A straightforward modern legal term.