The Student visa covers anyone enrolled full-time at a Japanese institution, from university degree programs to vocational (senmon) schools to private Japanese-language schools. Your school acts as your sponsor and applies for your Certificate of Eligibility, the same way an employer would for a work visa — see How to Apply for that process.
Duration is tied to your program length, typically issued in increments and renewed as you progress. Financial proof is usually the strictest part of the application: you (or a sponsor, often a parent) need to show enough funds or income to cover tuition and living costs for the duration of study, since the visa itself doesn't come with a right to work. See Financial & Income Requirements for what counts.
Students can work part-time with separate permission (a "permission to engage in activity other than that permitted"), capped at 28 hours a week during term time. Language schools in particular face extra scrutiny on this point, since part-time work limits are a known area regulators watch closely. Graduating doesn't automatically convert your status — moving into a work visa afterward means applying for Changing Status of Residence once you have a job offer.
Back to Visa Types.