HONGKONG'S Eastern know they will have to make the most of home advantage when they face Japanese champions Yomiuri tomorrow after learning about the reception that awaits them in the return leg in Tokyo. Yomiuri arrived in the territory yesterday for the Asian Club Championship first-round, first-leg clash and announced that the second leg next Wednesday was already a 65,000 sell-out. The news will have left the Eastern camp even more aware of the need to obtain victory tomorrow if they are to stand a chance of surviving the pressure-cooker atmosphere guaranteed to be generated by a capacity crowd in the Tokyo Olympic Stadium. Yomiuri's Dutch technical adviser, Frans Van Balkon, said: ''The return leg has already caught the imagination of Japan. All 65,000 tickets have been completely sold out. ''Eastern might have problems playing outside Hong Kong. The Hong Kong clubs don't have many chances to play away and they don't travel as much as, say, the European clubs.'' The Japanese are confident that whatever the result tomorrow, they will put up a good show in front of their home fans. Yomiuri, lying second in the J.League table, are considered Japan's most popular team and Van Balkon said they were accustomed to playing in front of huge crowds. Van Balkon, who was Hong Kong's national coach between 1975 and 1977, predicted tomorrow's clash - expected to attract a 8,500 capacity crowd to Mongkok Stadium - would be ''very close''. He added that Yomiuri were a completely different side to the one which knocked South China out of the same competition two years ago. Yomiuri will be relying heavily on their three foreign recruits, Brazilian striker Faria Barreto Bismarck and compatriot Luiz Carlos Pereira, who will be in defence with Dutchman Johannes Christian Van Rossum.