  Future e$^+$e$^-$ colliders, thanks to their clean environment and
triggerless operation, offer a unique opportunity to search for long-lived
particles (LLPs). Considered in this contribution are promising prospects for
LLP searches offered by the International Large Detector (ILD), with a Time
Projection Chamber (TPC) as the core of its tracking systems, providing almost
continuous tracking. The ILD has been developed as a detector concept for the
ILC, however, studies on understanding of the ILD performance at other collider
concepts are ongoing. Based on the full detector simulation, we study the
possibility of reconstructing decays of both light and heavy LLPs at the ILD.
For the heavy, $\mathcal{O}$(100 GeV) LLPs, we consider a challenging scenario
with small mass splitting between the LLP and the dark matter candidate,
resulting in only a very soft displaced track pair in the final state, not
pointing to the interaction point. We account for the soft beam-induced
background (from measurable e$^+$e$^-$ pairs and hadron photo-production
processes), expected to give the dominant background contribution due to a very
high cross section, and show the possible means of its reduction. As the
opposite extreme scenario we consider the production of a light,
$\mathcal{O}$(1 GeV) pseudo-scalar LLP, which decays to two highly boosted and
almost colinear displaced tracks. We also present the corresponding results for
an alternative ILD design, where the TPC is replaced by a silicon tracker
modified from the Compact Linear Collider detector (CLICdet) design.
