Didier Quoistiaux had been working as a painter and illustrator for years when Yumi Yay, his wife's employer, asked him if he wanted to illustrate a children's book. It was a leap of faith, as he had no experience with children's books at all. But he managed to bring the four colourful Yumi Yay friends to life in a magnificent way.

- When did you start drawing?
I have been drawing ever since I was a young boy. I won my first drawing contest when I was 7 years old. The theme of the contest, organised by a big newspaper, was 'London'. I won first prize and got to take my mom on a city trip to London.

My parents have always encouraged me to further develop my creativity. And all the people I met, all the friends I made over the years, always encouraged me to keep going, and taught me different techniques to develop myself. I specifically want to mention Laurent, my graphic design partner, and my wife Joëlle, who encourages me on a daily basis.

- How did you discover your passion for drawing?
I have always been an all-rounder, a man of many talents. I like to experiment with different techniques and make beautiful, personal (and personalised) creations. I have made both small and large artworks, but my first major encounter with painting came when I was around 18 years old, when I was introduced to the world of graffiti through a classmate.

- What is your working method? Do you work 'analogue', on paper, or do you also draw on the iPad?
I mainly draw on paper, but during my studies I also got acquainted with digital drawing techniques. You see, I'm a trained architect. Initially, I decided to study architectural design because of the combination of being able to learn different techniques and further develop my creativity. That was really important for me.

- What do you like about drawing?
Drawing characters and cartoons is a really unique experience. That is the style that suits me best. I am also a big fan of comic books, and of illustrations in general, but mostly I draw on paper first and then on a wall.

- What did you think when Team Yumi Yay asked you to illustrate the books?
I was a little surprised. Mainly because I had to step out of my comfort zone; I had never illustrated a book before. It was a wonderful and very educational experience. I know how important children's books are, also because I have children myself, Lucile and Amaury.

- Which one of the Yumi Yay friends is your favourite? And why?
I think Otti is very special. He's really an endearing elephant. He is strong and tough, but all that toughness hides a small, sensitive and emotional elephant... Something that many children and some adults will be able to identify with.

- Which figure was the hardest to draw? And which one was the easiest?
From a graphical point of view, Tika was the most complex figure to draw, but overall the Yumi Yay style is not really complicated. It's about expressing feelings quickly and instinctively to the children who read it; a combination of simple emotions and colourful artwork.

- What's your favourite story?
I find Tika's story very funny, because I like to make jokes myself, especially with my children (and vice versa, by the way). The character probably resembles me most, although I'm also pretty good at racing, like Finn!

- What was the hardest thing to draw?
Probably the tree house in Otti's story. But in the end, I am really happy with how it came out. Especially in combination with the beautiful spring colours.

- What is your favourite drawing? 
I love Otti's winter drawings. This can probably be explained by my passion for skiing and snowy landscapes. The scene of the big jump in Billy's story was also fun to draw… But I won't say anything else about that, because I don't want to spoil the ending!

- What did your children think of the books?
My daughter loves Otti the Elephant, while my son is a big Billy fan. Lucile is just learning to read and these books are ideal for her. She loves reading them, and that's really nice to see. Amaury loves searching for the little characters.

- Do you still have dreams, things you want to achieve as an illustrator?
This will definitely not be my last illustrating adventure. I'm already thinking about a new children's book... And who knows? Maybe Yumi Yay's circle of friends will expand and we will add more books to the series! In any case, I love the night lights and the way the covers can be changed is very creative and fun. Long live the world of Yumi Yay!