For the full understanding of baryon-baryon interactions in flavor SU(3), the ΞN interaction is the last missing piece of information. So far, we have revealed the ΛN interaction to be attractive (UΛ ≈ 30 MeV), and ςN interaction to be repulsive in the medium to heavy mass-number region. The ΛΛ bonding energy is weakly attractive. While we have a few experimental observations suggesting the ΞN interaction would be attractive, there still exist large theoretical ambiguities weather it is attractive or not. Experimental determinations on the existence of bound states of Ξ hypernuclei by observing bound-state peaks are strongly awaited. In this report, a new preliminary result on the missing-mass spectrum of a 12C(K-, K+) reaction, which strongly suggests the existence of Ξ-hypernuclear bound states, is presented.