Yes, you can wear shorts and tank tops. Maybe you could cover up a bit for visits to temples but generally, you don't go inside temples (in the same way to see a cathedral, you do into an enclosed building) so you can be relaxed about this. For men, shorts and tshirts no problem.

While you will not be barred from most places for wearing sleeveless shirts in Japan, they are generally considered informal or "undergarment-adjacent" in traditional Japanese social etiquette. Japanese culture tends to favor modest and "neat" attire; for women, showing shoulders, cleavage, or midriffs can be seen as overly revealing, especially in professional settings or rural areas. Men wearing tank tops or "muscle shirts" in public are often viewed as underdressed or "sloppy" unless they are actively exercising. When visiting temples and shrines, it is respectful to cover your shoulders as a sign of reverence. In 2026, major cities like Tokyo and Osaka are more accustomed to Western fashion, but you might still receive subtle stares or "judging glances" in more conservative neighborhoods. If you do choose to wear sleeveless tops during Japan's humid summers, it is wise to carry a light cardigan or "UV-cut" hoodie to layer when entering religious sites, upscale restaurants, or air-conditioned trains where social norms are more strictly observed.