12F was the alias commonly used by this Operator in his mercenary work. By his own account, he vacillated between different factions and was involved in the several famous battles over the past few years.

The few verifiable documents we have confirmed that 12F was indeed present for these conflicts, either as a regular mercenary or security for a local facility.

He joined Rhodes Island with Owl, having been admitted for his unique combat experience as well as his experience in general. Now a standard Arts Operator assigned to normal duty.

Assorted commercials for the mobile game Arknights. These short animations aired on TV and were posted to Arknights YouTube channel, while additionally shared via Twitter, advertising the game and associated events after its Japan launch. 
 
The list of the commercials are as follows (note that CMs without animation are not present and, for the ones with long and short versions, the longer version is taken into consideration)
 
1) Official Animation Trailer (アニメPV) [7 January 2020] 
2) Grani and the Knights’ Treasure (騎兵と狩人) [30 January 2020] 
3) EP05 Necessary Solutions (第五章「快刀乱麻」) [5 March 2020] 
4) Operational Intelligence (戦地の逸話) [25 March 2020] 
5) Heart of Surging Flame (青く燃ゆる心) [21 April 2020] 
6) Code of Brawl (喧騒の掟) [25 May 2020] 
7) Partial Necrosis (第六章「局部壊死」) [22 June 2020] 
8) Ancient Forge (洪炉示歳（エンシェントフォージ）) [22 July 2020] 
9) Stories of Afternoon (午後の逸話) [25 August 2020] 
10) Children of Ursus (ウルサスの子供たち) [25 September 2020] 
11) Twilight of Wolumonde (ウォルモンドの薄暮) [22 October 2020] 
12) Darknights Memoir (闇夜に生きる) [8 December 2020] 
13) The Birth of Tragedy (第七章「苦難揺籃」) [24 December 2020] 
14) Heart of Surging Flame - Rerun (復刻「青く燃ゆる心」) [18 January 2021] 
15) The Great Chief Returns (帰還！密林の長) [19 February 2021] 
16) Rewinding Breeze (在りし日の風を求めて) [22 March 2021] 
17) Maria Nearl (マリア・ニアール) [5 April 2021] 
18) Roaring Flare (第八章「怒号光明」) [21 April 2021] 
19) Mansfield Break (孤島激震) [18 June 2021] 
20) Beyond Here (彼方を望む) [2 July 2021] 
21) Who Is Real (画中人) [22 July 2021] 
22) Operation Originium Dust (オペレーション オリジニウムダスト) [13 August 2021] 
23) A Walk in The Dust (遺塵の道を) [28 September 2021] 
24) Under Tides (潮汐の下) [15 October 2021] 
25) Preluding Lights (灯火序曲) [6 December 2021] 
26) Dossoles Holiday (ドッソレスホリデー) [9 January 2022] 
27) Stormwatch (第九章「暴風眺望」) [15 March 2022] 
28) Pinus Sylvestris (赤松林) [11 April 2022] 
29) Near Light (ニアーライト) [21 April 2022] 
30) Break the Ice (風雪一過) [27 June 2022] 
31) Invitation to Wine (将進酒) [23 July 2022] 
32) A Light Spark in Darkness (闇散らす火花) [16 August 2022] 
33) Guide Ahead (吾れ先導者たらん) [13 September 2022] 
34) Shatterpoint (第十章「光冠残蝕」) [17 October 2022] 
35) Stultifera Navis (狂人号) [21 October 2022] 
36) Lingering Echoes (塵影に交わる残響) [23 December 2022] 
37) Ideal City: Endless Carnival (理想都市-エンドレスカーニバル-) [7 January 2023] 
38) Dorothy's Vision (翠玉の夢) [10 March 2023] 
39) An Obscure Wanderer (夕景に影ありて) [27 March 2023] 
40) Return to Mist (第十一章「淬火煙塵」) [24 April 2023] 
41) IL Siracusano (シラクザーノ) [15 May 2023] 
42) What The Firelight Casts (この炎が照らす先) [10 June 2023] 
43) Where Vernal Winds Will Never Blow (登臨意) [22 July 2023] 
44) A Death in Chunfen (春分) [18 August 2023] 
45) All Quiet under the Thunder (第十二章「驚靂蕭然」) [20 October 2023] 
46) Lone Trail (孤星) [4 November 2023] 
47) Hortus de Escapismo (空想の花庭) [18 December 2023] 
48) KFCコラボ [13 January 2024] 
49) So Long, Adele: Home Away From Home (火山と雲と夢色の旅路) [13 January 2024] 
50) The Black Forest Wills A Dream (樹影にて眠る) [23 February 2024] 
51) Come Catastrophes or Wakes of Vultures (ダーティマネー) [15 March 2024] 
52) The Whirlpool that is Passion (第十三章「悪兆渦流」) [12 April 2024] 
53) Zwillingstürme im Herbst (ツヴィリングトゥルムの黄金) [23 April 2024] 
54) The Rides to Lake Silberneherze (銀心湖鉄道) [18 June 2024] 
55) To the Grinning Valley (ニヤニヤ谷へ) [5 July 2024] 
56) Here A People Sows (懐黍離) [27 July 2024] 
57) Operation Lucent Arrowhead (オペレーション ルーセントアローヘッド) [2 September 2024] 
58) Babel (バベル) [8 October 2024] 
59) Absolved Will Be the Seekers (第十四章「慈悲光塔」) [26 October 2024] 
60) Path of Life (生存航路) [29 November 2024] 
61) Adventure That Cannot Wait for the Sun (太陽すらも追い越して) [12 January 2025] 
62) A Kazdelian Rescue (溶炉『還魂』 譚) [4 February 2025] 
63) Ending a Grand Overture (落日の向こうへ) [4 April 2025] 
64) I Portatori dei Velluti (幕開く者たち) [19 April 2025]

The newbie police officers Fang, Beagle, and Kroos were ordered to go to the slums of the Infected in the trading city of Tkaronto to do an internship. Although initially they had problems because of the crowdedness and other conflicts, they get accustomed to this and make friends with the Infected. While the end of their half-year internship, that would make them proper police officers, is nearing, a Catastrophe is quietly approaching the city of Tkaronto...
 
(Source: Official Site, translated)
 
Note: Chapter count includes one prologue and two bonus chapters.