Aliasing boku_to_goku_nee_to_umi_no_year!! -> boku_to_gonee_to_umi_no_year!!.
Reason: In the title, there is a small furigana (5)ねえ above the kanji 極姉. This gives the impression that 極 is pronounced "5" ("go") and not "goku". Also there are a few Japanese websites that use "go" specifically in furigana, but can't find any on search engines with "goku".
Updated by jxh2154