I'm sorry, but without really knowing the content of 'kondo koso shiawase ni narimasu light novel', it's difficult to recommend similar ones. However, some popular light novels with themes of self - discovery and achieving a positive state like 'My Youth Romantic Comedy Is Wrong, As I Expected' could potentially have some similarities in terms of character growth.
Not having read 'kondo koso shiawase ni narimasu light novel', it's a challenge to recommend similar ones. However, light novels that focus on personal transformation and the attainment of a positive goal could be in the same vein. For example, 'Sword Art Online' has elements of the characters growing and evolving through their experiences in a virtual world. If 'kondo koso shiawase ni narimasu' is about characters evolving to reach happiness, then there could be some loose similarities.
I'm not sure specifically as I haven't read it. It could be about a journey towards happiness, with characters experiencing various events that lead them to find their own form of happiness.
It might offer a unique and perhaps unconventional story. But without more context, it's hard to say exactly what makes it stand out.
You might be able to find it on some specialized manga raw websites, but be careful as not all of them are legal or reliable.
One similar light novel could be 'KonoSuba: God's Blessing on this Wonderful World!'. It also has a unique and comical story with interesting characters in a fantasy setting. Another option is 'Overlord'. It shares the aspect of having a protagonist in a different kind of world with their own special abilities and circumstances.
The main difference lies in its central theme. The focus on twintail transformation is not very common in light novels. It sets it apart right away.
Well, from what I know, identity is a big theme. The protagonist's change to having twintails is not just a physical change but also affects their sense of identity. Also, the theme of acceptance might be there. Accepting this new form and the consequences that come with it in the story world. And there's probably a theme of humor as well, given the rather unique concept of the light novel.
The light novel might have engaging characters. They could be well - developed with distinct personalities. For example, the protagonist's journey of becoming a twintail might involve interacting with other characters who either support or oppose this transformation, creating various story arcs.
The manga could stand out because of its exceptional art style or the depth of the emotional connections depicted. Maybe it also offers a fresh perspective on the yaoi genre.
One could be 'Himegoto'. It also has some unique and comical elements in its story.
I'm sorry, as I don't know what'sono mono nochi ni light novel' is really about, it's hard to recommend similar ones. But if it's a typical light novel, you could try 'Sword Art Online'. It has a great mix of adventure, action, and some elements of romance. Another one is 'Overlord', which is set in a fantasy world with an overpowered main character.