There are many such cartoons. For example, 'Romeo x Juliet' shows the love story of a boy and a girl in a fantasy setting.
You might consider 'Fruits Basket'. It has a charming story of love between a boy and a girl along with interesting character developments. 'Nana' is also a good choice, showing the complex emotions and relationships of young love.
I think it could be a cartoon with a lighthearted and innocent theme, maybe in a park or a backyard.
It could be a fantasy cartoon where the boy and girl have superpowers and use them to help others while staying strong and healthy. Or perhaps a story about them exploring nature and having adventures.
It might be a romance cartoon that focuses on the relationship and emotions of the horse girl in love. For example, with challenges and sweet moments in her love journey.
Maybe 'Kiki's Delivery Service' is what you're looking for. Kiki shows a lot of independence and bravery, which could be seen as acting like a boy in some ways.
Well, it might be a school-themed cartoon where they are celebrating success in a project or having a great time at a school event. Or perhaps they are on a vacation, enjoying new places together.
It could be a sweet and heartwarming story about their journey of getting to know each other, facing challenges together, and growing their love.
There are several manga like that. One could be 'Magical Girl Boy', where a boy gains the ability to transform into a girl through magic.
It could be a cute and peaceful cartoon where a little boy is sleeping soundly in his bed, maybe with a teddy bear by his side.
It could be a funny cartoon where a boy is happily eating his favorite pizza.
Well, it could be an adventure cartoon where the boy is jumping to overcome obstacles.