The highly-anticipated Sony Xperia Z4 is now finally official, as it made its formal debut without much fanfare in Japan.

While other OEMs such as Samsung and HTC unveiled their latest flagship smartphones at the Mobile World Congress (MWC) in 2015, Sony chose to skip the event and save its new-generation Xperia Z4 for later.

Rumors indicated that the Xperia Z4 would make its official debut on Monday, April 20, and the smartphone is now indeed official. Instead of a big, splashy unveiling as some would expect, however, Sony decided to quietly unveil the device in Japan. No information is currently available regarding the global launch of the new Sony Xperia Z4, and it remains unclear at this point whether a "Compact" version is also in the cards. If it is, the company made no mention of it at this point.

The Xperia Z4 is expected to hit retail sometime this summer, sporting a few improvements over its predecessor. Compared to the Xperia Z3, the new iteration boasts a more powerful processor, a better front camera, and a slightly slimmer and lighter body, but otherwise it's not very different.

The new-generation Sony Xperia Z4 features the same 5.2-inch full HD display of its predecessor, the same 3GB of RAM, and the same 32GB of internal storage capacity with microSD support for additional memory of up to 128GB. Under the hood, however, the new iteration packs the 64-bit octa-core Qualcomm Snapdragon 810 processor, which should deliver more horsepower.

In the camera department, the Xperia Z4 features a 20.7-megapixel rear shooter just like its predecessor, but the front camera is now more selfie-friendly with a 5-megapixel wide-angle lens sensor.

In terms of appearance, the Sony Xperia Z4 looks very similar to the Xperia Z3, retaining the same design language, but it's slimmer at 6.9 x 72 x 146 mm and lighter at 144g.

The Xperia Z4, however, also has a slightly smaller battery compared to its predecessor, packing a 2,930 mAh unit instead of the Xperia Z3's 3,000 mAh battery. As expected, the new Sony Xperia Z4 is also dust- and waterproof for extra durability. On the software side, the smartphone ships with Android 5.0 Lollipop out of the box.

As previously mentioned, Sony has only announced its new Xperia Z4 flagship smartphone in Japan, but the company should offer details on the global release, as well as pricing, soon enough.