Dedicated software is unnecessary

Several dedicated programs for creating a family tree are sold commercially, but spreadsheet software such as Excel is enough.

Create it in spreadsheet software

It is extremely simple and needs no explanation, but to create a family tree in spreadsheet software, adjust the widths of rows and columns, draw relationship lines with cell borders as appropriate, and write names and dates of birth and death (in both the Japanese era name and the Western calendar) and so on.

It is also useful to write down the date of marriage, place of residence and so on, which helps during field research and interviews.

If you want to add atmosphere, you can paste in an image of the family crest or use a brush-style font.

If you create it in Google Sheets, it may be convenient for checking from a computer or tablet during field research.

If you trace all lines of direct ascendants, the tree becomes quite large, so divide it by paper size, such as A4, and attach page numbers or reference numbers at the connection source and destination to make the connections easy to follow.

What about cloud services?

You can also use a free family tree website such as FamilySearch. With such services, you may be able to connect with people who share a common ancestor.