Sekai Ichi 

Japanese for "World's Greatest", or "Best in the World".

"BAKAMONO GA! DOITSU NO KAGAKU WA SEKAI ICHI!"
"You utter fool! German science is the best in the world!"

Sekai Ichi by Arky the Returd January 14, 2020

Sekai-Ichi Hatsukoi

Sekai-Ichi is a manga and anime by the author Nakamura Shungiku, who is famous for writing the anime and manga Junjou Romantica. She is a yaoi or boys' love author. Some of her other creations are √W.P.B. (2003)
Castilla (2000)
Hybrid Child (2005)
Junjou Mistake (2008)
Junjou Romantica (2002)
Junjou Romantica Artbook (2008)
Junjou Romantica dj - Chika*Chika 3)
Mangetsu Monogatari (2009)
Picturesque of a Mask (2004)
Restaurant Games (2003)
Sekaiichi Hatsukoi (2008)
Touzandou Tentsui Ibun (1998)
Tsuki wa Yamiyo ni Kakuru ga Gotoku (1999)
Umi ni Nemuru Hana (2001)
In the Sekai-Ichi Hatsukoi manga and anime, Usagi Akihiko is mentioned, as he is a character in her series, junjou romantica.

The ukes in Sekai-Ichi Hatsukoi are so cute!

The whats, in what?
Oh, never mind. You won't get it because you don't like yaoi.

Sekai-Ichi Hatsukoi by Moki-Chan November 13, 2011