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.
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.
One could be 'Himegoto'. It also has some unique and comical elements in its story.
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.
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.
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.
Some similar light novels could be 'Overlord'. It also has a strong isekai theme with the main character being very powerful in the new world. Another one might be 'That Time I Got Reincarnated as a Slime'. It involves a character being reborn in another world and gradually becoming very powerful.
Similar light novels? Well, 'Log Horizon' is set in a game - like fantasy world where characters have to deal with various situations and grow in power, which is a bit like what might be in 'saikyou no maou ni kitae rareta light novel'. Additionally, 'Grimgar of Fantasy and Ash' has a group of characters developing their skills and surviving in a fantasy world, which shares some common elements with the concept of being trained by a powerful entity as in the given light novel.
I'm sorry I can't recommend similar light novels as I'm not familiar enough with 'kawaiikereba hentai demo suki ni light novel' to make accurate comparisons.