There is a title for which only one game title has not been added when applying for the series.

Here it is https://www.speedrun.com/shugo_chara_3tsu_no_tamago_to_koisuru_joker

You need to request this through the support hub: https://www.speedrun.com/knowledgebase/supporthub/game-adjustment

Under the Sub-Category section choose "To Be Part Of A Series" and add your game there.