水原一平氏に関してはその後，新たな情報がありませんが，NBC ロサンジェルスの彼の"学歴詐称"に関する記事にあったのが，‘Peanut butter and Jelly’ relationship という表現です。
‘Peanut butter and Jelly’ relationship with Ohtani
The Diamond Bar High School website notes Mizuhara previously worked for the Boston Red Sox, interpreting for Hideki Okajima whose MLB career took place between 2007 and 2011.
Upon leaving Boston, Mizuhara went back to Japan to interpret for the Hokkaido Nippon-Ham Fighters of Nippon Professional Baseball (NPB), where he met Ohtani. Ohtani joined the Hokkaido team as a rookie in 2013.
When Ohtani signed with the Los Angeles Angels, he brought Mizuhara along with him.
Their professional relationship appears to have grown to a friendship. Mizuhara told Nippon.com that he and Ohtani hang out and play video games together off the field.
Former Angels Manager Joe Maddon told Kyodo News in 2021 that Ohtani and his interpreter went together like “peanut butter and jelly.”
When Ohtani signed a 10-year, $700 million deal with the Los Angeles Dodgers – the most lucrative contract the sport has ever seen –Mizuhara was also hired to continue to interpret for the baseball star. ESPN reported that Mizuhara told the outlet he had been paid between $300,000 and $500,000 annually.
‘Peanut butter and Jelly’ relationshipはもちろん比喩で，ピーナッツバターとジャム（ゼリー）を塗ったパンのように，「二人は息がピッタリの組み合わせ」という意味で用いられています（Ohtani and Mizuhara go together like peanut butter and jelly.）。
"These phrases are used to express a strong and complementary bond between two people, just like the combination of peanut butter and jelly."
私はそれほどハマりませんでしたが，確かにアメリカの同級生たちはパンにピーナッツバターとジャムの両方を塗ったパンを好んで食べていたように記憶しています。日本でいうと，さしずめ，あんとバター or ジャムとバター or あたりでしょうか。
似たような言い回しは，You're the salt to my pepper.，You're the sun to my moon.などを思い出します。
なお，同記事の水原氏の大学（UCR）の学歴詐称云々については以下のように簡単に述べられています。これもNBC LAの記事だけなので真偽の程は？ですが...。
ともかくも大谷選手の会見が待たれます。（UG）
The Japanese-language interpreter attended Diamond Bar High School, according to the school website. While some reports indicated Mizuhara graduated from UC Riverside, a spokesperson from the university told NBCLA there are no records of him attending the school.
