Sisu is something we like to see as a unique Finnish concept. Sisu is all about persistency, stamina and guts to do something. Maybe I'm a traitor, but I think quite many cultures and languages have a concept for such a willpower that makes one go even through a rock - so in that sense sisu may not be too unique, Finnish-only type of phenomenon.
Sisu is also a candy. And yes, it's called Sisu, not Gifu, the font is a bit misleading. As a candy I think Sisu is pretty unique, I've never tasted anything like Sisu candies. Sisu tastes a bit like liquorice mixed with a hint of mint or eucalyptus. Sisu candy also has a very characteristic smell, you can immediately tell if someone in the room has eaten Sisu. In mouth Sisu feels a bit like if you were having a piece of tyre in your mouth, and it looks like a piece of tyre too. Not that I'd have experience on tasting tyre, but I can imagine how it might feel like.
I've understood that Queen Elizabeth always carries a box of mint candies in her purse. Maybe Sauli Niinistö could equip himself with a pack of Sisu as a president of Finland. Congratulations Sauli and good luck for the new challenges! You will most likely need both sisu and Sisu.