the produced $^{10}_{\Lambda \Lambda}$Be is interpreted to be in the ground state, the resultant $\Lambda \Lambda$ bond energy becomes repulsive, contradictorily to the NAGARA event. From the viewpoint of the present study, the [*Demachi-Yanagi*]{} event can be interpreted most probably as observation of the $2^+$ excited state in $^{10}_{\Lambda \Lambda}{\rm Be}$; our calculated value of $B_{\Lambda \Lambda}(^{10}_{\Lambda \Lambda}{\rm Be}(2^+)$ ) is 12.28 MeV, which agrees with the above experimental value. This good agreement suggests that our level structures calculated systematically are predictive and useful for coming events expected to be found in the further analysis for the E373 data. Now it should be stressed that the above experimental data of $_\Lambda^{ }$$_\Lambda^{\!\!\!10}$Be$(2^+)$ leads to no information for the ground-state value of $B_{\Lambda \Lambda}$ unless the theoretical value (2.86 MeV in our case) of the excitation energy of $_\Lambda^{ }$$_\Lambda^{\!\!\!10}$Be$(2^+)$ is utilized.

On the other hand, the old experiment by Danysz [*et al.*]{} [@Danysz63] on the pionic decay of $^{10}_{\Lambda \Lambda} {\rm Be} (0^+)$ $\rightarrow $ $^9_{\Lambda}{\rm Be}(1/2^+)+p+ \pi^-$ gave $B_{\Lambda \Lambda}^{\rm exp} (^{10}_{\Lambda \Lambda}{\rm Be} (0^+))
=17.7 \pm 0.4$ MeV. This value has been used for a long time, which means the strongly attractive $\Lambda \Lambda$ interaction. However, it should 