[4] Being one of the best historians of the region, Sergii Osachuk devoted a lot of time to researching and writing scientific works, in particular about the history of Bukovyna.

One of the main emphases in his research was on the peaceful coexistence of different ethnic groups and cultures of Bukovyna, setting them as an example for today's generation of Bukovynians.

He repeatedly initiated discussions on the historical past of Bukovyna, inviting historians from Ukraine, Romania, Austria, and Germany.

At the same time, discreditation campaigns were regularly conducted against Sergii Osachuk, primarily by political rivals and groups trying to hinder his scientific work.

One of these campaigns was his accusation of not recognizing the mass shooting of Romanians in the village of Bila Krynytsia, although Sergii Osachuk stated that the shooting in Bila Krynytsia was a tragedy not only for the Romanian but also for the Ukrainian people.