What are RIKEN genes? I am using data from the Tabula Muris Consortium.

These are gene counts from scRNA-seq of mouse cells.

There are some specific genes with name ending with suffix 'Rik' (e.g. 0610005C13Rik or 0610007C21Rik). Searching online I found that they are from RIKEN project.

However, they are different in some respects (e.g. antisense lncRNA gene, or mouse 0610007C21RIK Adenovirus).

I want to exclude them from downstream analysis, but it is unclear to me the main purpose of this collection. For which kind of analysis are they used?
My understanding is that these are cDNA sequences from the RIKEN project that don't yet have another gene name. The project carried out a comprehensive sequencing of the mouse genome, and as a result found a lot of cDNA transcripts that were previously unknown. Now they have some annotation (which can be varying degrees of functional annotation), and an accepted official identifier to allow people to talk about these transcripts when discovered in other studies.

It'd be interesting to see if any novel transcripts have been found from the Tabula Muris project. They would also need their own identifier, possibly leading to similar intrigue about their history.