I don't know any Asian footballers besides Iranians who have been top scorers in a European league, I will name the ones I know from the top of my head help me if there are more: Current top scorers this season: Shahab Zahedi in Ukraine Sardar Azmoon in Russia Top Scorers in previous years: Mehdi Taremi in Portugal 2019/20 Sardar Azmoon in Russia 2019/20 Alireza Jahanbakhsh in Holland 2017/18 also a few more Iranian players have been top scorers in more minor european leagues like in Greece, Iceland, Azerbaijan and Albanian league. Honourable mentions Kaveh Rezaei 2nd top scorer in Belgium league, Reza gucci 2nd top scorer in Dutch league, Karim ansarifard 2nd in Greek league, vahid hashemian 3rd top scorer in German league. in good position to become top scorers this season besides the current top scorers I listed are son hiung min in England currently in join 2nd and Mehdi Taremi again in portugal currently in joint 2nd.
Well before Messi broke his record, the leading all time goal scorer(369 goals) for Spain's Barcelona FC was Philippine born Fil Spaniard Paulino Alcantara who played for them from 1912 to 1927 as well for Philippine club Bohemian Sporting Club from 1916-18 in the interim. He remains the youngest player at 15 y.o. to score a goal for Barcelona FC and is rated one of the club's biggest legends with his own alcove at Camp Nou dedicated to his memory. He also represented the Philippines in the 1917 Far East Championship Games where he helped the country give the worst thrashing to Japan in it's football history 15-2.