DoCoMo, which already holds 42.1 percent of the music store chain, will increase its stake to 50.3 percent by mid-July for an undisclosed price.
"By establishing Tower Records Japan as a subsidiary, NTT DoCoMo expects to capitalise on the envisioned growth of e-commerce triggered by the proliferation of smartphones and tablets," the mobile firm said in a statement.
Tower Records operates 89 stores in Japan, in addition to an online music shop.
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