TOKYO/OSAKA -- Japanese stationery king Kokuyo took a direct stake of 37.45% in compatriot Pentel on Tuesday, formally becoming its leading shareholder as the pen maker accepted the partnership after months of resistance.

Pentel's board gave the green light Tuesday for transferring the shares from a fund managed by Mercuria Investment. The transaction was completed the same day, making the pen maker Kokuyo's equity-method affiliate.

Kokuyo was essentially the largest shareholder, having invested 10.1 billion yen ($94 million at current rates) in the Mercuria fund in May. The stationery company sought to tap Pentel's overseas channels, as foreign sales make up less than 10% of Kokuyo's tally.

But Pentel initially refused to come to the negotiating table, fearing the loss of its independence. Company officials called the process behind the indirect investment "opaque" and said Kokuyo's actions were not conducive to building a trusting relationship.

Pentel ultimately changed course in an effort to fight a domestic sales slump. The pen maker's annual group sales total about 40 billion yen -- roughly one-eighth what Kokuyo reaps. Over 60% of Pentel's sales come from outside Japan, but a recent lack of hit products has left it suffering at home.

In a news release, Kokuyo said the two companies agreed to "begin negotiations toward building a collaborative relationship," adding that it expected the move to have only a "negligible" impact on group earnings for the current fiscal year.