In Japan, many clean restrooms, that can be used for free without asking staff, are available everywhere. In Japan, many clean restrooms, that can be used for free without asking staff, are available everywhere.

In Japan, there are many clean restrooms available everywhere that can be used for free without asking staff are available everywhere. In Japan, there are many clean restrooms available everywhere that can be used for free without asking staff.

Feels better in this order for some reason.

In Japan, many clean restrooms that can be used for free, without asking the staff. They are available everywhere. In Japan, many clean restrooms can be used for free, without asking the staff. They are available everywhere.

Although they aren't as clean as those in cities, parking areas with restrooms can be found even along roads in the mountains and alongmountain roads and the seaside. Although they aren't as clean as those in cities, parking areas with restrooms can be found even along mountain roads and the seaside.

During a visit to Hong Kong, Hong Kong Disneyland had Disneyland, there were clean restrooms available, so I didn't have to worry and could eat and drink freely. During a visit to Hong Kong Disneyland, there were clean restrooms available, so I didn't have to worry and could eat and drink freely.

However, in the city of Hong Kong, I was worried about suddenly needing to use the restroom, so I hesitated to eat and drink outside the hotel. However, in the city of Hong Kong, I was worried about suddenly needing to use the restroom, so I hesitated to eat and drink outside the hotel.

Even though there aren't many clean restrooms that are available for free, why don't people living there mind? Even though there aren't many clean restrooms that are available for free, why don't people living there mind?

They are accustomed to asking staff, "Can I use your toilet?", so they don't find it bothersome. They are accustomed to asking staff, "Can I use your toilet?", so they don't find it bothersome.

This sentence is grammatically fine, though in your previous sentence, you asked a question which you seem to be answering (or wondering about) here. Since this isn't a conversation between you and somebody else, you could preface it with something like "Well, it's because they are accustomed...". Or, if it's just wondering, "Perhaps they are accustomed..." or "I suppose they are accustomed..."