|Full name||OTs-12 Tiss|
|Country of Origin||Russian Federation|
|Manufacturer||TsKIB SOO (Central Design Bureau of Sporting and Hunting Weapons)|
|Voice actor||Yumi Uchiyama|
OTs-12 is an obtainable Tactical Doll in the game.
Experimental carbine developed in the early 1990s by TsKIB COO, OTs-12 Tiss (ОЦ-12 Тисс) "Yew Tree", literally a remodelled AKS-74U designed to chambered the 9x39mm sub-sonic round.
When compared to the AKS-74U, Tiss differs only in the bolt, barrel, muzzle-brake, and magazine, every other feature are practically identical. Gas-operated, rotating bolt operation, right side charging handle, magazine release behind the well just like all Kalashnikov derivatives. Tiss feeds on a 20-round box magazine and able to achieve a rate of fire of 800 rounds per minute, the 20-round box magazine was designed so that it would be compatible with standard current-issue ammo pouches, a larger 25-round magazine was planned before project's cancellation. With Tiss being built based on the AKS-74U chassis it would mean all the accessories available to 74U is compatible with Tiss, Warsaw Pact/Soviet Union issue accessories items such as clamp-mount for optics and the 30mm suppressed grenade launcher could be mounted on Tiss if it made it into service.
In 1993 a few hundred were built and delivered to the Russian Internal Troops for evaluation, Tiss achieved satisfactory performance, with the subsonic round showing superior penetration of cover at short and medium ranges (200–300 m) when compared to the 5.45x39mm. Despite that there just wasn't enough interest for Tiss to enter service in any branch of Russia's military, the production was cancelled later that year. Though performed excellently during the trial, but there were too many other weapon using the 9×39mm calibre munitions of that era such as 9A-91 and SR-3 Vikhr, which were more compact than a default AKS-74U chassis. With project abandoned TsKIB COO started the work on the successor project OTs-14 Groza. 
As a firearm Tiss never saw any form of live action (that we know off), items such as the hearing protection headset and plastic goggles she is wearing shows that she was strictly a laboratory project. Using the weapon as a comparison Tiss' body height is probably around 140 to 150cm.
Despite being a product made after the dissolution of the Soviet Union, the character design of Tiss still incorporated many Soviet symbols, such as the Hammer and Sickle imprint on her thigh high socks/stockings, Hammer and Sickle badge on her collar and beret, star shaped imprint on her tie and various star shaped hair ornaments.
A mysterious (Or she thinks she is a mysterious) T-doll, she constantly mentions that she is a secret weapon, at anywhere, to anyone and during any situation. She somewhat feels more superior just because of her being a secret weapon, though she understands her true ability limits well enough to not over step boundries or intentionally being provocative.
Very little information is revealed about her since she is a T-doll of mystery, no comments can be found reflecting her private lifestyle, hobbies nor relationship with other T-dolls. Being born from the same research facility and as a predecessor project, Tiss should be like an elder sister of AR OTs-14, but nothing this was mentioned in the game. Based on quotations from Tiss, she seems a little oblivious to things around her, such as checking for missing squad members after turning in the results of logistic missions.
High effectiveness rate of fire boosting skill boosts Tiss' damage output to be quite high in the early game stage, though her actual damage value is too low when compared to high rarity units. Grid buff provides rate of fire and firepower, suitable for firepower type SMG units.
It is ill-advised for new players to train high rarity T-dolls at the beginning of the game due to the lack of exchange cores, Tiss is one of the early game units players could consider making use of with her easy expansions and relatively effective skill.
Can be obtained as random combat reward from stages 5-5, 5-6, 6-4 7-4, 8-2, 8-4, 8-6, 8-2E, 9-2, 9-4, 9-6, 9-1E, 10-2.
|Acquisition||秘密武器“紫杉树”，正式报到，指挥官，需要更详细的介绍吗？||秘密兵器チーセス、到着！指揮官、もっと詳しい説明いる？||Secret weapon "Tiss", reporting in. Commander, do you need a more detailed description?|
|Introduction||以AKS-74U为原型改造的“紫杉树”，主要是为了特种行动而研发的微声突击步枪，装配有特别标识的微声子弹。因为是秘密武器，关于我的资料没有太多可公开的，不过……也可能是因为和原型很像，并不需要太多介绍了吧？||Modified version of AKS-74U, "Tiss". Low noise assault rifle designed mostly for special operation, equipped with the signature sub-sonic ammunition. Not a lot of information are declared about me, since I'm a secret weapon, well... Or maybe just too similar to the original model, there just isn't much to declare?|
|Secretary||那么……我近期的表现如何呢？||最近のわたしはどう？||Um... What do you think of my recent performance?|
|指挥官，有我的任务吗？||待ってるから。||Commander, do you have any tasks for me?|
|稍稍有点吵呢，是你在我身后吗，指挥官？那……没关系的……||騒がしいわね。さっきのは指揮官？ならいいわ。||Slightly noisy... Is that you behind me Commander? That fine then.|
|Secretary (post OATH)||
Had more cameos recently, all thanks to your attention on me... It's ok, there's no need to keep this happy thing secret.
Commander, is this... For me? Uh, don't apologize. I know of my value. But if I could become the greatest secret in your heart, it's good enough for me. Thank you Commander.
|Greeting||指挥官，今天要我出场吗？……没事，我明白，我是秘密武器，对吧？||わたしが出ようか？…あ、そっか、いいです、秘密兵器だから。||Commander, do I need to appear today?....Ah, it's ok, I know, I'm a secret weapon.|
|T-Doll Produced||新的同伴加入了，希望能活跃起来。||新しい仲間が来てるわ。||A new friend's coming.|
|Joining an echelon||嗯？不得不依靠我这个秘密武器了呢。||おお？秘密兵器に頼っちゃう？||Hmm? Had to rely on the secret weapon?|
|Enhancement||我明白，这是秘密改造，对吧？||分かってるよ、秘密改造ですよね。||Understood, a secret modification.|
|Dummy-linking||哦！指挥官，这样的待遇，果然您还是很重视我的！||やっぱ大事にしてくれますよね指揮官！||Of course I'm being paid attention to by the commander!|
|Logistics (start)||出门采购，嘘，要保密哦……||仕入れに行ってきます。||Beginning procurement.|
|Logistics (end)||我回来了，唔……大家都在吗？||ただいま…みんないる？||Coming back...Is everyone here?|
|Autobattle||这次是秘密行动吧，我会不留痕迹地搞定的！||秘密行動ですね、必ず果たします！||It's a secret operation this time, will get it done!|
|Starting a combat mission||要出发了，大家，准备好了吗？||行くわよ。みんな準備はいい？||We'll be going soon, everyone ready?|
|Starting a battle||“紫杉树”，突袭开始！||チーセス！突撃開始！||Tiss, begin combat!|
|Skill activation||确认目标，射击！||ターゲット確認、撃て！||Confirmed target, attack!|
|你们逃不掉的！||逃がさないよ！||You won't escape from me!|
|Heavily damaged||为什么会这样……我明明被寄予了厚望……||どうして…期待されてたのに…。||Why... I had high expectations...|
|Retreat||大家，对不起……我原本应该……发挥得更好……||こめんなさい…もっと…活躍したいのに…。||Sorry everyone... I should have performed better...|
|MVP||如何呢，指挥官，作为秘密武器的我，没有令您失望吧？||どう？秘密兵器のわたし。期待通りよね。||How was it? Did the secret weapon disappoint you?|
|Restoration||抱歉，希望我……下次还有机会……||ごめん、次があったら…。||Sorry, please give me another chance...|
|Halloween||今晚的气氛虽然不太适合秘密行动，但隐藏在这么多奇怪的家伙里，好像也很容易呢。||Tonight's atmosphere is not very suitable for secret operations, though maybe it is easier, if I stay hidden amongst those oddly dressed people.|
|New Year's Day||