Natsu is a popular female Japanese name. It is also a popular name element in many other Japanese female names such as Natsuko “summer child.” 夏子 made of the elements (natsu), “summer” and the popular feminine name suffix of (ko) meaning “child.”
Japanese pronunciation is hard to transliterate for someone who is a native speaker of one of the many Indo-European languages. The O in Natsuko is barely pronounced. It is somewhat akin to the American English pronunciation of the O in Deborah (DEB-ruh; DEB-o-RUH). Hence the pronunciation would be something akin to NATS–ko or NAT-so-KO.
There is also Natsuye, which is made up of the Japanese characters natsu “summer” and the suffix of ye, either denoting a branch or cove. So the name can either mean “summer branch” or “summer cove” and is pronounced something like (NAHTS–weh).
Another name made up of the natsu element is Natsumi, made up of the obvious natsu and the element of み (mi ) “beautiful”, .る (mi) “reality; truth” . Hence it could either mean, “summer truth” or “summer beautiful.” The pronunciation can be described as something like (NAHT-smee) or (NATSeh-MEE).