Can school time in Japan count for naturalization?
Some sites and people have claimed that certain types of 在留資格 (Status of Residence) for foreigners living in Japan do not count — such as a 留学 aka "Student" SoR — towards the continuous physical presence test of five (5), three (3), or one (1) year – depending on whether you qualified for regular naturalization (普通帰化) or simplified naturalization (簡易帰化) — requirement.
This is not true. All time spent legally in Japan, even on a 15/90 day visa-waivered temporary landing permit (TLP aka "tourist visa" ← a misnomer), can theoretically count towards the physical residency test.
However, if the bulk of your time was spent in Japan as a student, the odds of you getting successfully approved for naturalization are slim, in my opinion. Why? You must still pass the "livelihood requirement", which says:
自己又は生計を一にする配偶者その他の家族の資産又は技能によって生計を営むことができること。In other words, part of the naturalization process involves needing to convince the 法務省 (Ministry of Justice) that you have a decent chance of living, until you die, in Japan without ending up on welfare.
Translation: Being able to make a living through his/her own assets or abilities, or through those of a spouse or of another relative his/her making a living
Sorry, twenty-somethings: life in school does not count as "real life" or "making a living," no matter how hard your academics are and no matter if you didn't live in a dormitory or if you had a part-time job.
Of course, many people who have naturalized to Japanese did go to school in Japan. However, they probably did not use their time in school as the evidence of meeting the physical presence in Japan requirement.
