Multi-core connector, connector, and connector connection mechanism

A plurality of holes 7 are formed in a ferrule 3. The holes 7 are at sites penetrated by the tips of optical fibers 13. An opening 9 is formed in the upper surface of the ferrule 3 and an internal housing section 21 is exposed from the opening 9. The housing section 21 is at a site at which an optical fiber holding member 11 is housed. The optical fibers 13 are held by the optical fiber holding member 11. The optical fibers 13 are multi-core fibers. In other words, the optical fibers 13 have a specified axis of symmetry in a cross-section vertical to the longitudinal direction of the optical fibers 13 and have orientation relative to a rotation direction having the longitudinal direction as the axis thereof.