But SoftBank's investment approach means large transactions can cause unpredictable fluctuations in its results, said Mariko Semetko, senior credit officer at Moody's Japan
The Bengaluru-based company is aiming for a $50 billion valuation for its public listing as early as this year and was in talks in the United States for a deal with a blank-check firm, Reuters reported in March.
Investors were also scooping up large traditional Japanese companies, including Toyota Motor, which gained 1% to a record high, having risen 10 of the last 11 sessions.
Wall Street stocks finished little changed as renewed concerns about higher interest rates offset strong manufacturing data and a rally in petroleum-linked shares.
The benchmark Nikkei 225 index edged up 0.17 percent, or 46.78 points, to 28,364.61, while the broader Topix index rose 0.44 percent, or 8.35 points, to 1,913.04.
Takeda Pharmaceutical was up 0.16 percent at 3,774 yen after reports said Japanese authorities will likely this week approve the use of Moderna Covid-19 vaccines, which the Japanese firm will import.
The benchmark Nikkei 225 index fell 1.30 percent, or 392.62 points, to 29,696.63, while the broader Topix index was down 1.47 percent, or 29.20 points, at 1,954.34.
The Nikkei index, which on Monday closed above the 30,000 mark for the first time in about two weeks, extended its gain in early trade after Wall Street shares rallied to another record finish.