One popular 'To Love Ru Riko' fanfic could be 'Riko's Adventure'. It might explore Riko's character in unique ways, like her relationships with other characters in different settings.
Another option is to check out some dedicated anime fanfic forums. Sometimes, these smaller communities have hidden gems in the form of fanfics. They might not be as well - organized as the larger platforms, but you could stumble upon some really interesting and unique 'To Love Ru Riko' fanfics.
In a great Riko boyfriend fanfic, the emotions need to be on point. The love, the joy, the occasional sadness should all be palpable. It should also respect the original characters of Love Live. Riko should still retain her musical talent and her shy yet determined personality. And the fanfic should add something new to the existing Love Live universe, whether it's a new aspect of Riko's character or a fresh take on the relationships within the group while focusing on her relationship with her boyfriend.
One plot idea could be that Keita and Riko are in a band together. They start off as just bandmates, but as they go through the ups and downs of the music industry, they develop a deep friendship and then eventually fall in love. Their journey could involve dealing with record labels, jealous bandmates, and the pressure to succeed.
One common theme is friendship - turned - love. Usually, they start as friends in the fanfic and then slowly realize their deeper feelings. For example, they might support each other through school problems first and then those feelings transform.
The fanfic should also capture the overall tone of the series. Since 'To Love Ru' has a mix of humor, action, and some emotional moments, the fanfic should blend these elements well. For instance, having humorous exchanges between characters while also dealing with some deeper emotional issues that Nana might face.
I'm not sure about a specific one, but you can start by looking on fanfiction.net. There are often many well - written fanfics about 'To Love Ru Scientist Rito' there. You can search for ones with high ratings and good reviews to find some real gems.
There's a fanfic titled 'Riko and Maki's Adventure in Love'. In this story, they go on a journey together and along the way, they face various challenges that strengthen their bond. The author does a wonderful job of showing the emotional growth of Riko and Maki as they navigate their feelings for each other.
A fanfic could focus on a day in the life of Riko and Takuya. Maybe it's a normal rehearsal day. Riko is nervously preparing for a new piece on her euphonium, and Takuya notices her unease. He offers her some tips and words of encouragement. As they practice together, they start to understand each other's musical styles better. This could lead to a more harmonious playing between them during the actual performance. It could also be the start of a budding romance as they realize how much they enjoy each other's company.