Usagi and Mamoru could have a story where they volunteer together at an animal shelter. They bond over their love for the cute animals. One day, a little puppy gets sick and they work together to nurse it back to health. This shared experience makes their relationship stronger, and they realize how well they work as a team, which deepens their love.
Love is a very common theme. Since Usagi and Mamoru have a strong romantic connection in the original story, fanfictions often expand on their love, like how they overcome obstacles to be together.
In another scenario, Usagi and Mamoru could be at a ball. They dance gracefully together, lost in each other's eyes. After the ball, they take a stroll along the beach. The sound of the waves crashing against the shore sets a romantic mood. They hold hands tightly and exchange sweet nothings, reaffirming their love for each other.
Yes, there are likely some family - friendly Usagi Mamoru pregnant fanfictions. Some writers might focus on the more innocent aspects like how they prepare for the baby, the emotional changes in their relationship in a very pure way, without any inappropriate content.
Love and sacrifice is a common theme. Mamoru would sacrifice his time and energy to take care of Usagi. Another theme could be the power of friendship. Their friends would likely come to their aid during this difficult time. Also, the theme of hope. Despite Usagi being sick, there is always hope for her to recover and have a healthy baby.
The plot could involve Usagi's sickness being related to some sort of magic or enemy plot. Since she's pregnant, her powers might be affected. Mamoru, being the loving partner, searches for a cure while also protecting Usagi. There could be a lot of emotional turmoil as Usagi is worried about the baby and Mamoru is torn between finding a solution and being by her side all the time. Eventually, with the help of their friends, they figure out what's wrong and Usagi recovers, ready to give birth to a healthy baby.
One great 'usagi x mamoru fanfic' is 'A Starry Encounter'. It beautifully portrays their relationship with vivid descriptions of their interactions. The author does an amazing job of capturing their chemistry.
Some amazing usagi x mamoru fanfiction include 'Destiny's Bond'. This story really emphasizes the fated nature of their relationship. 'Love Beyond Time' is another good one where they are able to traverse different timelines to be together. And 'The Rose and the Moon' which uses symbolism of the rose (associated with Mamoru) and the moon (associated with Usagi) to tell a heartwarming story about their love.
You can find usagi x mamoru fanfiction on various fanfiction websites like FanFiction.net. There are a ton of stories there. Archive of Our Own (AO3) is also a great place. It has a large collection of fanfics with different ratings and themes. Another option is Wattpad, although the quality can vary more there.