Mysql slow query on large table

With Mysql 5.6.10, I have a table like this:

CREATE TABLE `es_user_action` (
  `id` bigint(11) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` bigint(11) unsigned NOT NULL,
  `company_id` bigint(11) unsigned NOT NULL,
  `work_id` bigint(11) unsigned NOT NULL,
  `action` tinyint(2) NOT NULL COMMENT '10, 20, 30, 40',
  `action_id` bigint(11) unsigned DEFAULT NULL,
  `apply_id` bigint(11) unsigned DEFAULT '0',
  `apply_display_id` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `action_time` datetime NOT NULL,
  `scout_time` datetime NOT NULL,
  `register_datetime_sorting` datetime DEFAULT NULL,
  `score` tinyint(2) DEFAULT '0',
  `is_pending` tinyint(2) DEFAULT '0',
  `apply_status` tinyint(2) DEFAULT '2' COMMENT '1: paid, 2: free',
  `has_response` tinyint(2) DEFAULT '0',
  `response_time` datetime DEFAULT NULL,
  `is_shown` tinyint(2) DEFAULT '1',
  `source` varchar(15) COLLATE utf8mb4_unicode_ci NOT NULL,
  `created_at` timestamp NULL DEFAULT NULL,
  `updated_at` timestamp NULL DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `user_company_work` (`user_id`,`work_id`,`company_id`,`apply_id`,`source`),
  KEY `IDX_2` (`company_id`,`is_shown`,`apply_status`,`apply_id`,`work_id`,`action_time`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=436896779 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

The full query I want to perform on the table would be the following:

SELECT
    `id` AS `seqNo`,
    `company_id` AS `companyId`,
    `work_id` AS `workId`,
    `action` AS `userActionType`,
    `action_time` AS `userActionDatetime`,
    `is_pending`,
    `apply_status`,
    `action_id`,
    `source`,
    `user_id` AS `userId`,
    `apply_display_id`  
FROM
    `es_user_action`
WHERE
    `company_id` = 449664
    AND `is_shown` = 1 
    AND `apply_status` = 1
    AND `apply_id` = 0
    AND `action_time` >= '2021-01-05 15:56:14'
-- AND `work_id` IN ( 1250160 )     
ORDER BY
    is_pending ASC,
    action ASC,
    score DESC,
CASE
        source 
        WHEN "entenshoku" THEN
        action_time 
    END DESC,
CASE
        
        WHEN source <> "entenshoku" THEN
        action_time 
END ASC
    LIMIT 100 OFFSET 0;

The table has around 15 million rows and the following query takes around 15 seconds. Can anyone help out? Thanks in advance.

UPDATED:

This is the explain query result:

UPDATED 4/2/2021:

Handler counts result: