If you have a passport issued by Romania which have visa exemption arrangements with Japan, your are NOT required to obtain visas to enter Japan. The period of stay granted at the time of the landing permission will be 3-month.
Many schools admit students all year round for a variety of classes(e.g. sushi, ramen, yakitori, tempura and more) ranging from a one-day private lesson to a 3-month course. You are able to stay in Japan and participate a course at culinary schools within 3-month without visa. Course will be held in English and Japanese language is NOT required.
If you want to stay more than 3-month to study, you are required to obtain student visa or cultural activity visa.
To know more about culinary schools in Japan