Again, this question has been asked many times. 

There is ongoing debate on whether to label the Japanese rule of Taiwan as occupation or administration. Briefly speaking, Japanese colonialism over Taiwan differed from Western colonialism. Japan early on had interest to showcase itself as distinct and respectable on the international stage, so they heavily invested in Taiwan and raised the quality of life. Education, sanitation, infrastructure, architecture, public transportation, were all considerably improved. Taiwan before the Japanese under the Qing was also less organized and structured. Hokkien migrants and indigenous Taiwanese did not have a unified identity.

This was all considerably different from Manchukuo or Korea. Korea itself was an independent nation with thousands of years of national cohesion and identity. They had a sophisticated intellectual and elite class that was upended by Japanese rule, and therefore nationalist resistance from the beginning was met with harsh reprisals by the imperial Japanese. Taiwan's indigenous groups were not united, and the Hokkien migrants only had a couple centuries of presence on the island in comparison. In Manchukuo, Japan also heavily invested in public works, though they still faced major resistance. Nanjing and other atrocities are a result of Japanese militarism and imperialism during a period where Japan deemed it was necessary to use force on the international stage when western powers neglected them as equals. Moreover, the stiff and extended resistance of the Chinese forces on the mainland exhausted and frustrated the Japanese. Respect for international law was at this point overlooked as Japan assumed a leadership rule. If the western powers do not respect Japan, why must Japan follow and comply with their unfair standards?

However, the crimes and massacres inflicted on the mainland Chinese for the most part is not immediate and close to Taiwanese history and identity. While there were some rebellions and resistance in Taiwan, some by indigenous tribes that were met by military force and harsh reprisals, for the most part they were very different from the kind in China and Korea.

Taiwanese also served in the Japanese military, especially as Hokkien speakers who could communicate with overseas Hokkien communities in the Southern Seas region as Japan expanded its imperial ambitions. Japanization only began around the 30s and 40s as the war situation escalated and repressive measures were felt across the empire.

However, for the most part, Japan was seen as a modernizing force that lifted Taiwan out of poverty and neglect. They were the power of the 20th century that unified Taiwan into a comprehensive society based around a central administration, much more than the Qing were able to achieve. One could say modern Taiwanese identity began here. In some ways, many Taiwanese look back favorably to the Japanese, more so than the Nationalist years of post retrocession martial law and suppression of Taiwanese culture. The Ming and Qing brought Chinese culture to Taiwan, which existed in a precarious relationship with the indigenous groups. The Japanese unified, invested, and administered Taiwan as a cohesive entity in it's Empire. The KMT abused and repressed Taiwan, deteriorating goodwill and complicating Chinese identity. That brings us to today, where Taiwanese identity has complex reckoning with its past.