One potential enemy could be developers. They might see the hot spring as just a piece of land to build on, not caring about the mc's new existence as the hot spring. Another could be rival natural attractions. If there are other hot springs or beautiful places nearby, they might be jealous of the mc's hot spring getting all the attention and try to undermine it in some way.
Well, it could be about the main character who is reincarnated as a hot spring. Maybe they can communicate with those who come to soak in them, like sharing the stories of their past lives or giving out some mysterious advice. And there might be some sort of adventure as the hot spring tries to protect its existence from those who want to develop the area or something like that.
There are several. One example could be 'The Reborn Hero's Love for the General', where the MC reincarnates and develops a deep affection for the general.
Some official fan communities dedicated to the source material of 707 and the MC might also have fanfic sections. These communities are a great place to find fan - created content, as the members are usually very passionate about the characters and share their own works or recommend others' works.
In 'Echoes of Separation', the MC's personal growth and changing priorities cause them to leave the ML. The character development is quite intense in this one.
You might want to check out 'Dragonborn'. The MC is a dragon who undergoes a journey of self-discovery and battles against powerful foes. The world-building and character development are really engaging.
There are several places to find '707 x mc fanfic'. First, check out the official forums or communities related to the original work that 707 and mc are from. Fans often share their fanfics there. Additionally, social media platforms like Tumblr or Twitter can be good sources. Sometimes, fans post links to their fanfics or even post short snippets directly. However, the most reliable places are still dedicated fanfic websites like AO3 and FanFiction.net as they have better organization and a wider range of content.