A full walkthrough and guide for the The Search for Oyamatsumi sidequest in Shin Megami Tensei V (SMT 5). Read on to figure out where to find the sidequest, how to complete it, and what rewards you can receive.

The Search for Oyamatsumi Location

The quest-giver is a Take-Minakata located closeby the Kanda-no-Yashiro Leyline Fount in the northern point of Chiyoda.

The Search for Oyamatsumi Sidequest Information

How to Complete The Search for Oyamatsumi

Objectives
1	Talk to Take-Minakata closeby the Kanda-no-Yashiro Leyline Fount. This quest appears after defeating Surt in the Hellfire Highway main quest.
2	Teleport to the Shiba Leyline Fount in the Minato region. Oyamatsumi will be the giant punished foe walking around the dunes closeby to the northwest.
3	Strike Oyamatsumi to engage with them in battle. Defeat Oyamatsumi to fulfill the quest objective. ・How to Beat Oyamatsumi
4	Defeating Oyamatsumi will reward you with a Kunitsu Keystone. Return this item to Take-Minakata to end the quest. You will receive 1 Balm of Life and 22000 EXP as quest rewards.

How to Beat Oyamatsumi

Hit its Weaknesses

Oyamatsumi is weak to Fire and the Mirage status ailment. Exploit these weaknesses to secure more turns for yourself.

Cast Tarunda Every Turn

You should cast Tarunda on Oyamatsumi at least once in every turn to lower Oyamatsumi's attacks. This strategy can help you last longer in the fight as Oyamatsumi will deal lesser damage on your party.

Defend Against Ice Attacks

Use demons who don't have a weakness to Ice. It would be ideal to use demons that block Ice, which will make Oyamatsumi lose its turns. Otherwise, you can use Ice Dampeners or Makarakarn to block Oyamatsumi's Ice attack.

Take Advantage of Omagatoki: Critical

This Magatsuhi skill can save you a whole round without having to consume MP. Or you can use it to extend turns so that you can concentrate on healing and debuffing. After you've cast your attack-blocking skills, go all out with your fire attacks on Oyamatsumi.

Full Guide:
How to Beat Oyamatsumi

Shin Megami Tensei V Related Guides

List of Subquests and Rewards

Vengeance Subquests

Subquests
Prince of Her Dreams	In Pursuit of Knowledge
Brawny Ambitions	She Who Rules the Night
Knocking on Death's Door	Beastly Battle of Wits
Home Sweet Home	To New Horizons
Picture-Perfect Debut	Essential Research
Brawny Ambitions II	Infiltrate the Demon Feast
Tough Love	Pixie on the Case
As God Wills	A Self of My Own
Part-Time Gasser	Lighting the Way
Reclaim the Golden Stool	Liberate the Golden Stool
A Star is Born	Shinjuku Jewel Hunt
The Disgraced Bird God	The Vampire in Black
The Hunter in White	Alice's Wonderland
Devotion to Order	Heroes of Heaven and Earth
The Serpent King	The Great Adversary
Supersonic Racing	Classified Courier
Song of Nostalgia	Guide to the Lost
Rite of Resurrection	Heroes of the Celts
The Guardian of Light

List of SMTV Vengeance Subquests

Da'at: Minato

Subquests
A Preta Predicament	No Stone Unturned
Bully Breaker	Pollution Panic
The Spirit of Love	The Water Nymph
The Cursed Mermaids	The Demon of the Spring
To Cure a Curse	The Gold Dragon's Arrival
The Benevolent One	The Ultimate Omelette
Talisman Hunt	Movin' on Up
Keeper of the West	The Succession of Ra

Da'at: Shinagawa

Subquests
Chakra Drop Chomp	Those Seeking Sanctuary
Holding the Line	A Wish for a Fish
Magic from the East	Can I Keep Them?
Iced Out	Kumbhanda's Bottle
Birds of a Feather	The Tyrant of Tennozu
The Root of the Problem	A Goddess Stolen
The One I Love	The Falcon's Head
Keeper of the South

Da'at: Chiyoda

Subquests
The Path to Myojin Forest	Lighting the Way
Black Frost Strikes Back	A Sobering Standoff
Stones of Malice	One Mokoi's Trash...
He of a Hundred Hands	An Unusual Forecast
A Power Beyond Control	The Search for Oyamatsumi
Clash with the Kunitsukami	The Horn of Plenty
Roar of Hatred	Glitter in Ginza
The Angel of Destruction	The Ancient Guardian
Keeper of the East

Da'at: Taito

Subquests
On Bended Knees	Downtown Rock 'n Roll
The Egyptians' Fate	A Princess in a Pickle
In Defense of Tokyo	The Raid on Tokyo
A Need for Nectar	Abaddon's Assault
Keeper of the North	The Bull God's Lineage
An Incentive for Incense	The Destined Leader
The Holy Ring	The Sleeping Sands
The Winged Sun	Fionn's Resolve
A Universe in Peril

Empyrean

Subquests
The Seraph's Return	The Red Dragon's Invitation
The Noble Queen	The Wrathful Queen
The Compassionate Queen	A Plot Revealed

DLC Quests

DLC Subquests
A Goddess in Training	The Doctor's Last Wish
The Rage of a Queen	Return of the True Demon
Sakura Cinders of the East	Holy Will and Profane Dissent