Siro is a large x-height sans-serif family for text designed by Ryoichi Tsunekawa, and the whole family consists of 7 weights from ExtraLight to Heavy and their matching Italics. 
The basic skeleton of their letterform was designed simply to create a neutral, natural, and clean impression. And their very large x-height makes this family legible and readable even on a small size screen. 
Siro supports almost all European languages: Western, Central, South Eastern Europeans, and Afrikaans. 
And proportional figures, superior figures, inferior figures, denominators, numerators, fractions, ordinals, and case-sensitive-forms can be accessed by using OpenType features.