When you are traveling in Europe, you may know "Schengen Visa Countries".
It is important to consider these countries, because Japanese people can stay maximum for 3 months in Schengen Countries, with sightseeing visa.
According to below page,
Bosnia and Herzegovina,
are not Schengen Countries
By the way, remember UK is in EU, but not in Schengen Visa Country.
Japanese can stay for maximum 6 months with sightseeing visa.