TOKYO — The diplomatic thaw between Tokyo and Seoul may be recent, but major South Korean banks Shinhan Financial Group and KB Financial Group have been building relationships in Japan for years — and they are looking for more.

“In the future, we’re going into wholesale banking — that is, for corporate customers,” said Jin Ok-dong, CEO of Shinhan Financial, whose Japanese retail banking unit, SBJ Bank, marked its 14th year in business this year.

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