When conducting keyword research, you need to find out the search volume of your target keywords. Search volume is a very basic number for SEO. There are some free ways to find out, but since it is a very important indicator, I recommend using a paid tool.
I mainly use Google Keyword Planner. You cannot apply for the tool by itself, and you need to be running a paid campaign with Google Ads. I use many keyword tools in combination, but Google Keyword Planner is the most accurate and the fastest to reflect the search volume of new keywords.
SEMrush, Ahrefs, MOZ, Keywordtool.io, Mangools, and Dragon Metrics are also commonly used by companies.
Also, when using keyword tools, it is important to compare them with the same keyword tool. Especially in the case of Japanese, search volume often differs greatly depending on the keyword tool. The presence or absence of spaces often changes the value by several thousand units, and search volume fluctuates considerably for keywords that mix katakana, alphabets, kanji, and other characters.
Also, for some keywords, it is not possible to check the search volume. For example, keywords related to medical care often do not show up on keyword tools. If search volume for a well-known keyword does not appear, it is possible that the search volume is not disclosed for some reason.