This is the 11670th most frequent German word.
sumi
"Sumi" is not a standard German word. It might be a name or borrowed term.
Here, 'Sumi' is used as a proper noun being mentioned as a personal name.
Sumi ist ein japanischer Name.
Sumi is a Japanese name.
In this case, 'Sumi' represents the special ink used in East Asian calligraphy.
Die Tusche für die Kalligraphie wird manchmal Sumi genannt.
The ink for calligraphy is sometimes called Sumi.
'Sumi' here is being used as the subject's name, who is performing the action in the sentence.