The former official of the ministry's local bureau, Toshio Akagi, was forced to get involved in falsifying official documents related to a sale of state-owned land to school operator Moritomo Galuen at well below market value. Akagi killed himself in March 2018, five days after the document tampering was revealed.

The transaction sparked allegations of favoritism, as Prime Minister Shinzo Abe's wife was named as the honorary principal of Moritomo's planned elementary school.

Also on Wednesday, Akagi's widow revealed his suicide notes and memoirs through her lawyer.

One of the memoirs was dated on the day Akagi took his own life. In it, he said the ministry's financial bureau was involved in everything.

Akagi said he believes instructions came from former Finance Ministry bureau chief Sagawa.

Akagi said rank-and-file officials strenuously resisted a ministry proposal to revise the documents, because they could be viewed as giving favorable treatment to the school operator.

Akagi said he would take responsibility as the one who knows the truth.

Another memoir touched on the time when Abe's government was being grilled by opposition parties over the land transaction.

Finance Minister Taro Aso and other senior officials initially denied the existence of official documents related to the deal, but later admitted to it.

Akagi described their explanations as being "obviously false," as he said he and his colleagues had been instructed not to disclose the documents, including records of negotiations with the school operator.

Launching the legal action, Akagi's widow said she wants to know who gave the instructions and what kind of false claims were made at the Diet, in order to ensure that something like this will never happen again.