The appointment follows a series of electronic system failures since last year that led to the resignation of the group's CEO, its chairman and the head of its main banking unit.
Mizuho also reported measures to prevent system failures to Japan's banking regulators, including increasing the number of technology staff, after the bank was reprimanded for "undermining the credibility of Japan's bank settlement system".
"Following the series of system failures, Mizuho is at a crucial point," Kihara told reporters at a press conference. He will pursue his job "with strong determination", he said.
On Feb. 1 Kihara, 56, will replace Tatsufumi Sakai, whose nearly four-year tenure has seen shares of Mizuho fall about 16% compared to a 16% rise in the Tokyo market over the same period despite a cost-cutting drive.
Kihara, a graduate of Duke University School of Law, joined one of Mizuho's predecessor banks, Industrial Bank of Japan, in 1989 and also worked at the group's securities arm. He is the elder brother of Japan's deputy chief cabinet secretary Seiji Kihara.
Mizuho also appointed Seiji Imai, the head of Mizuho's corporate banking business, as its new chairman to replace Yasuhiro Sato in April.
(Reporting by Makiko Yamazaki; Editing by Chang-Ran Kim and Kenneth Maxwell and Kirsten Donovan)
By Makiko Yamazaki