OVA 1:
In the midst of his everyday life, Rimuru suddenly realizes that there's nothing to do for recreation in Tempest. He suggests sumo wrestling as a way for everyone to have fun together, and his friends are immediately on board with the idea. Thus begins Tempest's first sumo tournament, in which everyone competes enthusiastically in hopes of winning the grand prize! Passionate contests break out not only among Benimaru and the men, but also among women like Shuna and Shion, and even Rimuru ends up joining in!

OVA 2:
One day, Shuna and Shion are fighting over Rimuru's squishy slime body as usual. Rimuru figures that giving them each a body double of himself would solve the conflict, but when he imagines some of his other friends asking him to do the same for them, he quickly drops that plan. Then he comes up with the idea to make a cushion in the shape of his slime form. He travels around Tempest to see if his friends know of any good materials he can use, and he learns that a special type of sand found along a lakeshore in the forest is exactly what he's looking for. So he sets out to collect some sand... but a monster is waiting for him by the lake! What's more, Milim hears about his plan for a picnic and comes racing down from the sky!

OVA 3-5:
Rimuru, now a teacher at the Freedom Academy in the Kingdom of Ingrassia, has become involved in the school's outdoor training event with his class. The outdoor training event is an annual competition in which the students of each class guard the teachers on a journey to a nearby town. Rimuru is assigned to Class A, while his own students in Class S escort the young Tiss-sensei. All the students are eager to show how much their daily training has paid off, but the situation turns around when they're attacked by thieves!

(Source: Crunchyroll)

Note: Bundled with the limited edition of the 12th-16th manga volumes.

Action
Adventure
Comedy
Drama
Ecchi
Fantasy
Hentai
Horror
Mahou Shoujo
Mecha
Music
Mystery
Psychological
Romance
Sci-Fi
Slice of Life
Sports
Supernatural
Thriller
Light Novel
Manga
Original
Other
Video Game
Visual Novel
Achromatic
Achronological Order
Acting
Adoption
Advertisement
Afterlife
Age Gap
Age Regression
Agender
Agriculture
Ahegao
Airsoft
Aliens
Alternate Universe
American Football
Amnesia
Anachronism
Anal Sex
Angels
Animals
Anthology
Anti-Hero
Archery
Artificial Intelligence
Asexual
Assassins
Astronomy
Athletics
Augmented Reality
Autobiographical
Aviation
Badminton
Band
Bar
Baseball
Basketball
Battle Royale
Biographical
Bisexual
Body Horror
Body Swapping
Bondage
Boobjob
Boxing
Boys' Love
Bullying
Butler
CGI
Calligraphy
Cannibalism
Card Battle
Cars
Centaur
Cheerleading
Chibi
Chimera
Chuunibyou
Circus
Classic Literature
College
Coming of Age
Conspiracy
Cosmic Horror
Cosplay
Crime
Crossdressing
Crossover
Cult
Cultivation
Cunnilingus
Cute Boys Doing Cute Things
Cute Girls Doing Cute Things
Cyberpunk
Cyborg
Cycling
DILF
Dancing
Death Game
Delinquents
Demons
Denpa
Detective
Dinosaurs
Dissociative Identities
Dragons
Drawing
Drugs
Dullahan
Dungeon
Dystopian
E-Sports
Economics
Educational
Elf
Ensemble Cast
Environmental
Episodic
Ero Guro
Espionage
Exhibitionism
Facial
Fairy Tale
Family Life
Fashion
Feet
Fellatio
Female Harem
Female Protagonist
Firefighters
Fishing
Fitness
Flash
Food
Football
Foreign
Fugitive
Full CGI
Gambling
Gangs
Gender Bending
Ghost
Go
Goblin
Gods
Golf
Gore
Guns
Gyaru
Handjob
Harem
Henshin
Heterosexual
Hikikomori
Historical
Human Pet
Ice Skating
Idol
Incest
Inseki
Irrumatio
Isekai
Iyashikei
Josei
Judo
Kaiju
Karuta
Kemonomimi
Kids
Kuudere
LGBTQ+ Themes
Lacrosse
Lactation
Language Barrier
Large Breasts
Lost Civilization
Love Triangle
Mafia
Magic
Mahjong
Maids
Male Harem
Male Protagonist
Martial Arts
Masochism
Masturbation
Medicine
Memory Manipulation
Mermaid
Meta
Military
Monster Boy
Monster Girl
Mopeds
Motorcycles
Musical
Mythology
Nakadashi
Nekomimi
Netorare