Tokyo for 6 days -- tattoos

I will be in Tokyo from March 17-23 of this year and was hoping for some suggestions. I am on a budget and plan to do a lot of people watching. Are there any especially good places to do this? Are there any indoor places with good people watching as it may be cold?
Also, I am going with my boyfriend and we are both moderately tattooed. Is there anything we should be aware of in terms of customs? (I have also posted a question about this in the customs section).
In terms of gardens or great landscape views, are there any in particular you would recommend?
We are planning to go to Yokohama for one day. Is there anything in particular I should do there? We are visiting the tattoo museum and probably visiting a tattoo studio, which will take up some of our time, so any spectacular things we must see/do?
Thank you!!

Please look under the sections at the very top: travel, living, Japan A-Z to find aswers to many questions. For people-watching it is the same as in any big city: railway stations (Shinjuku station is used by about 2.5 million people a day..enough for you?) major department stores and underground malls,churches (here they are shrines and temples) and parks. Harajuku is a hang-out for young people

for tattos there is a post way down on the main questions page. Onsens are usually not keen on tattoos..

Hi, if you are visiting Yokohama, then please visit Sankeien garden which is a beautiful Japanese landscape garden with several traditional houses (some relocated from Kyoto)of the important cultural assets.
The best way to go there is from the JR Ishikawa-cho station(Motomachi exit). You can take a taxi from there. Or you go to the Sakuragisho station and take a bus from there. Also, I recommend you to visit Motomachi, China town, Yamashita Park,Red-brick warehouse, and Minato mirai area in Yokohama.
If you are having your tattoo done in Japan, it is best to contact a tattoo shop in advance. You may need to book for it beforehand.

Thank you both very much for your suggestions. I will definitely check out the garden in Yokohama.