Well, 'Re:Zero − Starting Life in Another World' might be a relevant choice. Just like 'ore twintails ni narimasu light novel', it involves a main character in a strange new world dealing with various challenges. And then there's 'The Rising of the Shield Hero'. It has a story that is full of adventure and character development, much like the style of many such light novels.
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.
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 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.
One could be 'Himegoto'. It also has some unique and comical elements in its story.
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.
One similar light novel could be 'Overlord'. It also features a powerful character in a fantasy world setting, much like 'maou to ore no hangyakuki light novel'.
Well, it might have unique characters. Maybe the storylines are centered around the concept of a guy becoming a twintail, which can lead to some really interesting and comical situations.
There might be some fan - made translations floating around on the internet. Try searching on light novel forums or groups on social media platforms. They may be able to point you in the right direction for a good translation.
One light novel that might be similar is 'Kimi ni Todoke'. It has a similar theme of relationships and feelings. The story focuses on a girl who is often misunderstood as scary, but then she starts to develop relationships with others. Another could be 'My Youth Romantic Comedy Is Wrong, As I Expected'. It delves into the complex relationships and thoughts of the characters, much like how 'ore wo suki nano light novel' might do.
One similar light novel could be 'Toradora!'. It also involves complex relationships between the main character, a girl he has a relationship with and other friends. The story is full of humorous and heart - warming moments.