Here was a critical moment in the endgame.
And then, it proceeded with ▲R*82 △P*42 ▲Rx81+ (Diag.2).
▲Rx81+ was not threatmate. On the next, with ▲G*31 △K-22 ▲Gx21 △K-13 ▲S*22 △K-24, it would not be mated. Therefore, it seemed like △G*89 was severe in Diag.2 because this move was threatmate with △Gx88 ▲Gx △S*89 ▲K-99 △P*98, but, the challenger Itodani was preparing ▲G*31 △K-22 ▲N*69 (Diag.3) in the variations.
▲N*69 means that sente removes gote's threatmate and is aiming to gain the gold on 89. If sente gain a gold in hand, the threatmate with ▲Gx21 △K-13 ▲S*22 △K-24 ▲G*25 will occur this time. Thus, Moriuchi couldn't play △G*89 in Diag.2 instead of △Gx34.
Sente might get a won position at ▲P*59 already.
While I was writing this article, the game ended. The challenger won the 1st game. I'm really looking forward to the rest of the match.