Softbank CEO Masayoshi Son says he and Alibaba's Jack Ma send each other drawings to keep in touch

• Alibaba founder Jack Ma and Softbank CEO Masayoshi Son send each other drawings to keep in touch.
• Their friendship stretches back years, and both have served on the board of each other's companies.
• Son said they've kept in contact amid Ma's Ant Group IPO bust and subsequent rumored disappearance.

Alibaba founder Jack Ma and Softbank CEO Masayoshi Son send each other drawings as a way to keep in touch, Son said on an earnings callon Monday.

Son said they've kept tabs on each other as reports have swirled surrounding Ma's rumored public disappearance in recent months.

He said their correspondence doesn't always involve business - Ma "likes to draw" and has sent Son "many drawings," the Softbank CEO said on the call. He said he responds to them with some bedtime artwork.

"Thirty minutes or so, before I go to bed, I draw some drawings ...[and] show him," Son said.

Ma and Son have kept a tight friendship over the years, with Son describing him as "my friend and comrade in my life." He also said he and Ma would meet "face-to-face every month to have dinner" before the COVID-19 pandemic set in.

Both have served on the board of each other's companies. Ma was a director at the Japanese investing giant for 13 years until he resigned last summer without explanation.

Son left Alibaba's board in June 2020 as well following Ma's departure. "It's not that there were disagreements," Son said in a general shareholder's meeting. "It is just a happy ending."

Softbank poured $20 million into Alibaba in 2000, an investment that reaped major rewards for the firm. Softbank is Alibaba's largest shareholder, holding a 25% stake in the company, and sold a little over $2 billion of that in June.

Ma has had a tumultuous few months following the bust of his company Ant Group's would-be record-breaking $37 billion IPO in November. After publicly scoffing at China's banking rules, officials summoned Ma to a regulatory meeting and introduced new micro-lending rules that disqualified Ant for a dual listing. China ended up pulling the IPO altogether.

The country has since ordered Ant to "return to its payment origins," and the fintech firm is currently working on a restructuring plan with China.

Read more: China's antitrust probe into Alibaba could be an opportunity for other cloud players - including Amazon, Microsoft, and Google - to swoop in

China's tech companies at large have seen a tighter crackdown since last fall. The country announced new rules in November that could prevent internet companies from holding too much market power. The regulations were designed to set stricter anti-competitive behavior guidelines.

China announced in December that it was launching an antitrust investigation into Alibaba over alleged monopolistic business practices.