Does Darius Trifarian see himself when he is played and is considered second played card?

Yes, Darius, Trifarian does see himself as the second card played in a turn and can trigger his ability to ready himself and gain +2 might.

According to the Riftbound rules and FAQs regarding this interaction:

• Darius counts himself: In Riftbound, a card is considered "played" once it has fully resolved and entered the board. Because Darius is already on the board when his "When you play a second card" ability checks, he is able to see himself as that second card.
• Triggering the effect: If you play Darius as the second card of your turn, his ability triggers, granting him +2 might and readying him (if he was exhausted).

Sequence of events:

1. You play your first card of the turn.
2. You play Darius, Trifarian as the second card.
3. Darius resolves and enters the board.
4. Darius's triggered ability checks the game state, sees that he is the second card played this turn, and triggers.
5. Darius gains +2 might and readies himself.

As noted in the Riftbound FAQs (e.g., FAQ #7847, #7793), this interaction is consistent because "Play" means "Resolve," and Darius is present on the field to witness his own resolution. Note that this only works if he is exactly the second card played; if he is played as the third card or later, the ability will not trigger.