Travelling with a companion, or not to travel with a companion.
I'd say firstly, it depends on your attitude and level of Japanese. Also, it depends a lot on how you typically travel. For instance, if you travel an average of once or twice a year then by all means bring someone with you for good company and to enhance the experience. But, if you are cataloging your experiences, and spending a lot of your time immersed in writing and photography then in my opinion going it alone is far better than with someone, unless you are climbing Mount Kilimanjaro or going on a dangerous expedition somewhere. Being able to read, write, speak, and understand Japanese is a must if you travel deep in the sticks. I do not recommend using English.
Being able to read kanji is a must because there are few signs in English. This is my opinion only. Sure, there are people who travel Japan with absolutely no knowledge of Japanese and they get by just fine. However, to be literate in the language of the host country is a far more enjoyable experience in my experience. Being able to understand what you are eating, and where it came from as opposed to eating something you don't know and having no idea where it came from, is not my style. Being able to converse with the front desk on various topics related to travel is better than not being able to understand nor converse with them at all. To be able to hail a taxi and communicate with the driver where I want to go is better than just pointing my fingers at a map and saying "here here!"
The soloist is a guy who isn't looking for the romantic get away spot. He/she is in search of information and contact with other people. He wants an intimate experience with his surroundings only. I want to feel my camera in my hands. I want to smell every single tiny little blade of grass I walk over. I want to get a feel for the whole of nature while totally caring nothing about anyone else. That's the soloist.
The soloist is the type of guy/gal who can linger around in a hot spa for ages and not be pressed for time, because of dinner appointments or scheduling complications. He can also spend as much time doing absolutely nothing at all and not offend anyone else. The soloist remembers what was eaten for dinner because it was the food that was communed with and the sake and not a none essential element such as a stranger or a person. The soloist has muted his anxieties from the constant stairs from packs of old grannies who see him or her sitting in golden silence.. There is nothing as wonderful like existing in such a peaceful state. The table in front mines, there was a soloist in his 40s, a Japanese gentleman. He was on his 4th sake and feeling good it seemed. He could splurge as much as he wanted because he had no care in the world. The rarest thing I saw was a white girl in her 20s traveling solo. She was staying at a deluxe hotel in Gunma Prefecture. She was sitting there alone at her big table full of food and she was wearing a yukata ( Japanese gown). She looked content. I was traveling with someone else at that time.
According to contemporary trends In Japan, the soloist is frowned upon as a social faux pas. A soloist whether male or female is seen as a bit dangerous, aloof and unsociable. A misfit so to speak. These trends have been changing though. It is not uncommon nowadays to see male and female soloist. I see them more frequently nowadays and it's good. Hotels have become more accommodating by offering special packages for the soloist. This could be due to the changing demographics, and the number of single people rising. Always inform the hotel of who you are and your travel status. It's a courtesy.
I learned from Takayama-san years ago. He and I had absolutely nothing in common. Whenever he took me out to an onsen he rarely spoke with me. He was a man of few words and never wasted his time on gossip or adult related topics. He would just look over at me and say " that is low energy!" I began to pick up a lot from him because he was the lone traveler who showed me the way. In modern day societies people would rather settle for the conveniences of home rather than going out to stay in a hotel. This is a natural consequence of modernization. In other words, people have forgotten why people go out anymore and this is not good. There is just simply no comparison with your home bathing unit to a natural hot spa in nature.
The purpose of this post should not be taken to mean "you should travel alone." I just feel I need to lend some perspective on travel from a guy who travels solo sometimes for the sake of clarity if anything. Being a soloist can sometimes be dangerous like when I drove through a snowstorm from the Tokachidake Mountains of Hokkaido to Sapporo and my GPS was out and with no visibility and on an unmarked road with a quarter tank of gas left in my tank and no gas station in site. Or, when I got stuck up on a mountain at midnight and saw howling wolves encircling my perimeter from the headlights. I was able to clear just enough room on the road from a fallen tree to edge my car through and made it to safety. I haven't blogged about that experience until now I think.
What you have to take from life's lessons is that time waits for noone. You have to make your own moves and then people will help you along the way. Not " I'm going to wait for people to show me the way." Maybe for some people. At any rate, to solo or not to solo is a decision that you clearly have to make based on your needs, and what your purpose is. If you are the carefree type that's not too caught on travel and need a companion then by all means bring a buddy or two. I have travelled in groups and have enjoyed myself immensely.