this is what i understood and the ideas that came to my mind when reading it
Shujin Body of Shadows
(Innate) Shadows Reach: Shujin can place shadow traps on nearby impassable terrain that arms after a brief time, becoming camouflaged last 60 seconds. when an enemy champion approaches, it activates sending a shadow tendril towards the champion location that roots the first enemy champion hit for 1 second.
casting range: 200
tendrill range: 450
Notes: its better to add a form of interaction than to just restrict the ability that much it becomes either too good or too bad. in your current iteration, not only it feels bad for you because the trap has only 200 range but also for enemies because in the case they activate the trap, they have no way to counter it, they just get rooted instantly. the idea is that the tendrill works like illaoi or lucian Q that they strike on where the character was at the moment of cast.
(Q) Kuni: Shujin throws a blade forward, dealing his total attack damage to the first enemy hit. Kuni behaves like a basic attack, applies on hit effects, can critically strike and counts as a ranged attack.
Kuni critically strikes for a modified amount agaisnt immobilized (root/entangle) targets.
CD: 3 seconds (maybe reduced by attack speed like yasuo' trust)
range: 900
**Notes:**the skill basically is a skill shot gangplank parley that works as a ranged attack instead of melee. i find it interesting because of the possible interations with items like hurricane, i imagine the skillshot firing the hurricane bolts to nearby enemies around the target struck by the blade. i think its a intersting abilily with lots of interations.
(W) Shadows grasp: Shujin lashes a shadow tendrill in a line that roots the first enemy champion struck and Shujin as well for the same duration.
If Shadows grasp hits terrain, it will create a shadow tendrill at the location. Additionally if Shadows grasp hits a shadow tendrill, it gains additional range and will lash out against the closest enemy champion entangling instead and without causing Shujin to root himself if the target is hit.
range: 800
shadow tendrill additional range: 450 (total 900 range)
shadow tendrill entangle: 1.5 seconds
root: 1.5-3 seconds.
**Notes:**i really liked this ability because of how important positioning is for Shujin, as a range character, you can play around to stay within attack range or use Q as much as you can aswell for also critical strike bonus and the fact that also immobilizes you makes you think twice before using it. Also came to mind the ability to combine it with his innate to help him abit further and also give him the chance to get rid of the root on himself if he founds the shot.
(entangle is a better version of a root, aside from rooting (cannot use displacement effects, flash, dashes, etc), the target cannot attack. currently the only champion with this type of crowd control is amumu).
(E) Dusk (renamed from Tactical Explosive): Shujin burst a target path in shadows dealing damage to every enemy in a line and slowing them. the shadows can be cast in a vector in any direction from any point within range.
Notes: this would be his main tool for laning phase as well as help him with cs, even tough hes a adc.
I think the ability is fine tough it can maybe become much more, the only thing i think can help is add a slowing effect to help him find the place and moments to better land the rest of his abilities.
(R) Shadow lock: Shujin instantly extends a shadow coil agaisnt the immobilized (root/entangle) champion aiming to their hearth, dealing damage and entangling them for 1.5 seconds. if the target is below 25% of their maximum health while affected, shujin pulls the tendrill, dashing towards the target and instantly execute them.
Notes: while this ability suffers the same as Dusk (Tactical Explosive) it can also become something more interesting. the only thing i found ideal for it to make it a commitment for him is by placing him in a dangerous position in exchange of executing the enemy, also dont know if it would be better as a player choise making it a second cast like with Urgot or that the ability continues if the rule triggers.
overall this feels like a illaio and vek'loz fusion but still kind of unique. Hope you find the suggestion interesting.