Honestly, 35mm is generally more practical for Tokyo because of the tight urban spaces. Since you are on an A7C, you really want to prioritize weight without sacrificing the sensors resolving power. I have looked at the MTF charts and real-world performance for several options under $600 and the Sony FE 35mm f/1.8 SEL35F18F usually wins out for pure versatility. Here are the technical specs that matter for your trip:

• Weight: 280g (keeps the setup balanced on the small A7C frame)
• Minimum focus distance: 0.22m (excellent for close-up food or detail shots)
• Field of view: 63 degrees (wide enough for architecture, tight enough for environmental portraits) If you find 35mm too wide and 50mm too tight, the Sony FE 40mm f/2.5 G is a fantastic technical compromise. Its incredibly light at 173g and the optics are very sharp across the frame even wide open. It fits the A7C aesthetic perfectly and wont feel bulky during long days of walking. You lose a little bit of light gathering, but for day shooting it is a solid choice. Another decent option if you want to save some cash is the Samyang AF 35mm f/1.8 FE. It is lighter and cheaper, tho the autofocus motor isnt quite as snappy as the native Sony glass. If you are doing a lot of night shooting in Shinjuku, that f/1.8 aperture is gonna be way more useful than an f/2.5. Tbh, id go with the native Sony 35mm f/1.8. It just works well for almost every scenario.