Complex sentence: Whilst in Japan, de Havilland, discovered the game of go, and became quite obsessed with it; although not the first Westerner to take up the game, he was the first to be considered a competent player.
Split into simpler sentences: Whilst in Japan, de Havilland, discovered the game of go, and became quite obsessed with it. Although not the first Westerner to take up the game, he was the first to be considered a competent player.