The New York-based lower middle-market firm has grown from seven to 12 employees with the additions.
Takahashi has nearly 30 years of private equity experience, particularly in the industrials and technology sectors.
Mallah joins from Sagard, where he worked as a managing director and head of MENA.
Mario Giannini, the firm’s executive co-chairman, will relinquish his duties next March after helping build a platform that manages and advises on more than $1trn of assets.
Masumi Waida has more than 20 years of investment management experience, including a previous CFO role at Fortress Investment Group's Mount Kellett Funds.
Baratta joined Blackstone in 1998.
The hybrid capital firm provides middle-market businesses with capital positioned between traditional debt and equity.
The UK firm invests in technology and specialist services businesses from its £411m ($544m; €478m) sixth fund.
Walsh, a former US Navy intelligence officer, was previously managing partner of FON Advisors.
Joseph, a former consultant at Boston Consulting Group, Accenture Strategy and Kurt Salmon, advises the firm's portfolio companies on operational performance.